Bedrock Edition Far Lands



The Far Lands were the area that formed the "edge" of the "infinite" map in Java Edition versions prior to Beta 1.8. They are currently found in the Bedrock Edition.

Lоcation
The initial set of Far Lands occur between 12,550,821 and 12,550,825 on the positive X and Z axes, and always -12,550,825 in negative.

A second set of Far Lands overwrite the first set after surpassing approximately 1,004,065,920 blocks, or almost exactly eighty times the distance of the initial set of Far Lands.

Structure
Both areas of the Far Lands feature extremely strange terrain, although they are significantly different.

In both zones, any area beneath sea level, excluding regular caves, will be flooded with water. The Far Lands will generate biomes but most biomes will be indistinguishable except by the color of grass. Desert biomes will be covered in sand and snow-covered biomes will be covered with snow, excluding the very top of the map due to the height build limit. Trees will generate somewhat normally, but can only be found in the upper areas of the map due to the need for grass. However, if you open the debug screen, it will always claim that the biome is a forest.

Ores can be found up to their respective maximum heights just like in the normal world. Unfortunately, due to the flooding, everything except for coal can be extremely difficult to acquire. In the solid areas of the Far Lands, normal caves will generate but will be limited and small. Along with the caves, dungeons (which are extremely rare) and lakes can be found in solid areas. Water and lava springs can be found out in the open and in caves.

Much of the open space in both areas is shrouded in darkness and thus hostile mobs run rampant, making the Far Lands as a whole incredibly dangerous. This is especially problematic in the Corner Far Lands due to its layered structure. The flooded zones have an abundance of squid.

Edge Far Lands
The boundary of the Far Lands' edge (that is, where it meets the regular map) looks like a solid wall, all the way to the top of the map (Y-coordinate 127) that is filled with gaping holes perpendicular to the edge. These holes are extremely long, perhaps "infinite", and on the whole seem to change very little no matter how deep the player ventures. They can be blocked, either partially or completely, but such blockages are rare and temporary. This "Wall of Swiss cheese" pattern continues beneath ground level, all the way to the bottom of the map, and seems to be partially caused by a large one-dimensional distortion in the map generator's output. This area is sometimes referred to as "The Loop".

The Edge Far Lands' average block composition: 36% stone, 25% air, 23% water, 10% dirt/grass block, 2% bedrock, and 4% others. (Based on a 14×14 chunk selection)

Corner Far Lands
At a corner, when two perpendicular Edge Far Lands sections meet, the Corner Far Lands begin to generate. Unlike the infinite-length holes in the Edge Far Lands, the Corner Far Lands contains more normal terrain. This terrain is "stacked" on top of itself to create a bizarre sandwich with layers of ground and air, which gives it its nickname, "The Stack". Each layer looks like a gigantic floating continent, hovering over the next layer, which is shadowed.

The majority of the generated world is Corner Far Lands, as the "normal" map (before ±12,550,821 mark) only makes the center of the world, and the Edge Far Lands only make its continued sides.

The number of layers isn't always the same, and varies between five to seven (fusing together and splitting every so often). Layers can be grouped into three categories: Sometimes, there are extremely tall pillars of gravel that stretch from the ground to the ceiling of a layer. Likewise, some of the beaches that collapse will create pillars of sand all the way down to the ground, despite there not being that much sand to begin with. The Corner Far Lands is also prone to having near-perfect diagonal lines being carved into the ceilings or floors of layers. If traced, these lines all intersect at the corner (X/Z ±12,550,821). This seems similar to how the Edge Far Lands have a consistent pattern along lines perpendicular to their edge, but is much less pronounced.
 * Top layer: This layer exists at the absolute top of the map. Occasionally there can be a lower area that isn't shadowed (this is technically a dry layer). The lower area is where a majority of the trees and passive mobs can be found, as the top layer receives almost all of the sunlight. Due to the lack of space the area at the absolute top can't have trees or mobs.
 * The top layer tends to light incorrectly in day-night transitions. This is because the sunlight calculation doesn't work when the entire chunk is blocked at Y-coordinate 128.
 * Dry layers: These generate slightly flatter than normal terrain and have grass, despite the darkness. At sea level massive floating beaches can be found, which will collapse if modified. Hostile mobs' spawn rate likely approaches the maximum due to being in the shadow of the top layer. Rarely, there are holes in the top layer that allow sunlight to reach these layers. Caves that have one of these layers as their "surface" can occasionally be carved out of dirt instead of stone. These layers have cave-like ceilings made out of stone, gravel and dirt.
 * Flooded layers: Like the dry layers, these generate somewhat flat terrain, but it is comprised primarily of stone. Sand and sandstone will show up down here, even up to 30 meters below sea level. Except for coal, all the ores can only be found in these layers.

The Corner Far Lands' average block composition: 40% stone, 16% air, 28% water, 10% dirt/grass, 2% bedrock, and 4% others. (Based on a 14×14 chunk selection)

Farther Lands


A second set of Far Lands (henceforth named the "Farther Lands") generate at approximately X/Z: >±1,004,065,920, or 80 times as far out as the initiation of the Far Lands. The Farther Lands completely overwrite the existing sets of edge and corner Far Lands, and have a more stretched-out and streamlined appearance than the earlier counterparts. The resultant Corner Farther Lands have remarkably flat terrain in comparison to the Corner Far Lands, with caves being almost the only disturbances. The Farther Lands generate exclusively within fake chunks.

No further sets of Far Lands have been discovered or calculated.

Floating Point Precision Errors (X/Z: ±16,384 - ±2,147,483,647)
There are many effects that will be noticed after traveling millions of blocks away from the center of the map. The very first effect that will be noticed is the jumpy or stuttering movement of the map, which isn't directly related to the Far Lands themselves but instead to floating-point precision errors. This jumpy movement is notable even at an X/Z of ±16,384, becoming increasingly noticeable around ±524,288. The intensity of such glitches doubles every time the player passes a coordinate that is a power of two (e.g 2,097,152 or 4,194,304). At X/Z 16,777,216 the world will be two whole blocks off and will continue to double, all the way until blocks stop rendering at X/Z 2,147,483,647. At the center of the Minecraft world, the world would only be off by $1/4194304$ (0.000000238...) blocks. Past the 32-bit limit the world would be off by 256 blocks. For any position between n and 2n, where n is a power of 2, the world will be offset by $n/8388608$ blocks, or $n/524288$ block pixels. If terrain were to theoretically generate out to the 64-bit Limit (X/Z 9,223,372,036,854,775,807) then the world would be over 2.2 trillion blocks off and redstone dust would be 2.2 trillion blocks wide as well.

Far Lands (X/Z: ±12,550,821 - ±2,147,483,647)
Players will experience extreme framerate drops and very high CPU usage, which will continue until Minecraft freezes completely. The framerate drops do not occur in multiplayer servers, though it will, depending on the server computer's RAM, make the server itself lag. In both singleplayer and multiplayer, the intense lag that is characteristic of the Far Lands is caused by massive numbers of falling sand or gravel entities. This in turn is caused (like most of the rest of the Far Lands' strange effects) by more floating-point precision errors, and will worsen as the player reaches X/Z: ±32,000,000 (Because after X/Z 32,000,000 the terrain no longer generates. Only air blocks that have the same textures as the surrounding terrain will generate.) Weather is not affected by the Far Lands directly but is by their terrain. Lightning bolts that hit surfaces at the top of the map (Y-coordinate 127) will be invisible and will not cause fire. The particles created when rain hits these surfaces will be black instead of blue. Snow will not accumulate on these surfaces either (because there's no space).

Fake Chunks (X/Z: >±32,000,000)
As the player journeys even deeper into the Far Lands, the effects worsen to the point where the game is unplayable. At X/Z ±32,000,000 blocks are treated as permanently nonexistent, and will not generate, even though they may appear to. Only air blocks that have the same block textures as the normal terrain will appear. This makes the terrain appear to keep generating, even though it technically doesn't. If the player tries to walk on these blocks, they will fall into the void. This value is hardcoded in the source code of Minecraft, meaning that it cannot be changed without editing the source files. Because the terrain doesn't technically generate beyond X/Z 32,000,000 things like trees, falling gravel, falling sand, mobs, grass and other entities will not generate either. This can make the map relatively stable and crashes can be somewhat rare, however crashes can happen on low end computers. In rare cases, if the player performs the "ghost spawn glitch" that worked in versions between Alpha 1.1.0 - Beta 1.7.3, you can cause trees and plants to generate beyond ±32,000,000.

World Render Limit (X/Z: ±268,435,456 - ±2,147,483,647)
At excessive X/Z positions (depends on the operating system, but usually occurs between X/Z: ±268,435,456 and ±2,147,483,647), world render glitches out resulting in terrain that will appear to flicker. This does happen X/Z: ±268,435,456 and gets worse every power of 2 beyond that. This could most likely be that past X/Z: ±268,435,456 the Minecraft world is 32 blocks off, which is as large as 2 Minecraft chunks, though it is unconfirmed.

32-bit Integer Limit (X/Z: >±2,147,483,647)
At X/Z: ±2,147,483,519, blocks are no longer rendered, giving the way to an empty sky. At X/Z: ±2,147,483,647 (maximum 32-bit Integer), the game will very likely crash or the player will get stuck. However, chunks will still generate along with clouds. Fast graphics clouds are however insanely stretched. Note that only 64-bit machines are able to pass this point.

Cloud Render Limit (X/Z: ±25,769,803,000 - ±25,769,804,000)
Between X/Z: ±25,769,803,000 and X/Z: ±25,769,804,000 clouds stop rendering (Varies between maps, but they disappear somewhere in between these distances. Does not apply for fast graphics clouds). Beyond here, only the sky, sun, moon and void remain.

Chunk Overwrite Limit (X/Z: >±34,359,738,368)
If one makes it to X/Z ±34,359,738,368 (235), chunks will start getting overwritten. As a result, this is the end of chunk generation in Minecraft. As soon as this limit is approached, the game will freeze and crash, resulting in an Out of memory screen. However in some cases the player may be able to move past this limit for a few seconds before Minecraft crashes. A chunk is 16 x 16 so it's likely due to the fact that Minecraft's chunk generation is also 32-bit, as 2,147,483,648 x 16 = 34,359,738,368.

64-bit Integer Limit (X/Z: >±9,223,372,036,854,775,807)
The highest signed value for 64-bit machines is X/Z ±9,223,372,036,854,775,807. However, despite this being the limit any machine can go, it may not be possible to reach anywhere near this point, since the vast majority of people experience instant client freeze, followed by the client crashing. In some cases, it is possible to teleport to it however insanely difficult. If one manages to make it this far, the only thing that will exist are the Sun and the sky, as shown by one user (see video below) that managed to actually be out this far.

Previously, there was a theory that at this distance there would be no sun, the sky would be pitch black and the clouds would glow oddly. This has since been debunked as false.

Alleged further distances
In late 2017, a video surfaced on YouTube by user Michu Mich that showed the player teleporting to extremely far distances trillions and trillions times over the 64-bit limit, the highest being a distance of X: 1084 (one septenvigintillion blocks), which was far over the 64-bit limit. It is unknown how this user managed to even get this far, since all the most powerful machines generally crash at the limit where chunks get overwritten, or in very rare cases the 64-bit limit. This brings the recorded distance into question and hard to verify despite video proof – no machine known to mankind as of 2018 is known to handle such an extreme distance without the game crashing or the computer itself locking up. It is possible the user may have used software running on 512-bit data, as the highest signed integer possible on a machine this powerful would be 1.3 x 10154. The user in question stated that he used a program called MultiMC with the most allocated RAM possible. However, despite this, the distance is very hard to verify, as the distance may have easily been manipulated using a modification.

Vertical effects (Y: <-2,147,483,647)
In Beta 1.7.3, as the player falls below Y -2,147,483,647, the darkness of being in the void disappears. Instead of darkness, the void now looks like an empty world. It has a sky, a sun, and a moon, and they are all visible depending on the time of day. Despite this, the player will still receive damage from the void.

Map editors
When viewing the Far Lands in a 3D Minecraft map editor, you will encounter errors. In MCEdit, the selection cubes start to distort and the map distorts when viewing. In addition when rotating your view around a selected area, blocks will not be lined up right and will change how poorly lined up they are randomly, making the whole world seem to shake like a machine about to rattle itself to pieces.

Previous versions
In Infdev, on the first version, extreme glitching happened at extreme coordinates, but the Far Lands did not generate. In Infdev (March 27, 2010), although the Far Lands existed, many of the side effects didn't. However, fire particles and doors would act strange. There was no stuttering movement, and beyond X/Z ±32,000,000, the blocks would simply not render. Walking off the edge would cause the player to become stuck in a glitched position, unable to escape.

In Indev (the release of January 30, 2010), the flat land bordering the map stops rendering at X/Z ±2,111, and the sky stops rendering at X/Z ±2,560. If the player steps onto the blocks beyond X/Z ±262,148, the game crashes. However, in some versions of Indev, using an NBT editor, the player can go to even further distances. Every exponent of 2 that you go, your hitbox becomes more and more distorted. At X/Z ±8,388,608, the player will fall through the blocks. The hitbox becomes increasingly more corrupted and distorted until it disappears entirely at X/Z ±2,147,483,648. The farthest distance you can traveled using this method X/Z: 10128 though you could go further. If you teleport to this distance in the version of Indev that does push you back to the map, you will be pushed from X/Z: 2128 to X/Z: 2,147,483,648 in about 5 minutes. As you are pushed back the Sun and Moon begin to render back in (Most likely at X/Z: 9,223,372,036,854,775,807) and then the game crashes at the 32-bit Integer Limit.

It has been confirmed that in Alpha v1.1.2, the blocks would not render beyond X/Z ±32,000,000, like older Infdev versions. The fake chunks started appearing in Alpha v1.2.0. In previous versions of the game, if you teleport as high as you possibly can, you are sent to a Y-Axis of 3.4x1038. In this zone, you float without a purpose, and dropped items will slide with what appears to be no friction before suddenly stopping after about 20 blocks. It has been reported that the X and Z-Axis sometimes flicker randomly in this zone. The memory pie chart also sometimes randomly jumps to 100% undefined memory usage, and then disappears upon re-entering the debug menu.

Java Edition, post-Beta 1.8
The X/Z Far Lands was fixed from this version, so they will not exist without modifications to Minecraft.

Location
On the X and Z axes, the Far Lands and Farther Lands initiate as they did previously, with an identical chance of offset at positive positions. However, they are actually 256 blocks tall, instead of 128.

On the Y axis, the Far Lands initiate at around twice the former number, which is therefore ±25,101,648. Since blocks obviously cannot exist above y=256 or below y=0 in the vanilla game, to observe the Far Lands in their natural habitats, mods such as the Cubic Chunks mod must be used to allow terrain to generate in such positions.

These positions can be changed using a Customized world; changing the Coordinate Scale to a higher value will cause the edge Far Lands to generate closer to the origin, and respectively changing the Height Scale will cause the sky Far Lands to come down. Unlike the edge Far Lands, the sky Far Lands exist in the vanilla game and will appear in the world without mods if a sufficiently high Height Scale value is used.

Farther Lands on the Y axis most likely do exist, however they have not been investigated in sufficient detail yet.

Structure
The edge Far Lands and corner Far Lands, as well as their Farther variations, generate relatively identically to their pre-b1.8 counterparts, but utilising the entire height limit, causing them to generate all the way up to y=256, or in the case of infinitely high worlds, until they reach the sky Far Lands at y=+25,101,648 (and equivalently the void Far Lands at y=-25,101,648).

Sky Far Lands
The Far Lands will generate at positive values of the Y-axis past y=25,101,648. Monoliths theoretically can generate up to these.

Void Far Lands
The Far Lands will generate at negative values of the Y-axis past y=-25,101,648.

These do not seem to be obtainable without using mods in the same way as the sky Far Lands.

Since every air block outside of caves and other generated structures is replaced with water below y=63, the void Far Lands are filled with water.

Vertex Far Lands
When the Sky or Void Far Lands meet with the vanilla Corner Far Lands, many interesting terrain features can be sighted. The content of these intersections appears to vary throughout worlds, with some being completely blank, some completely solid, and some generating like regular far lands material. In some cases, exciting diagonal patterns with large absent chunks will generate.

Floating-point precision errors with entities and particles
Even in modern versions of Minecraft, the floating-point precision errors still exist, but only with entities. Mobs will spawn and move along grids, which has cell edge's length doubles at every power of two of the corresponding axis. They tend to move to the nearest intersection of two perpendicular lines of grid. Other entities and particles (except items and entities, particles spawned using comands) are also spawned on that grid, for example a block of TNT when being ignited is "snapped" into another location, on the grid.

Locatiоn
The Far Lands will initiate after ±12,550,824 as in the Java Edition, however only on phones and Nintendo Switch; in the Windows 10 and Xbox One Bedrock ports, terrain just cuts off to reveal bedrock and ocean.

Structure
The Bedrock Edition Far Lands are different from the Java Edition Far Lands, specifically:

The content of the Far Lands in the Bedrock Edition is slightly different in biomes and structure in positive coordinates. Sand and gravel don't fall from generating in Bedrock Edition. This results in relatively stable performance.

In the Windows 10 Edition, the traditional Far Lands do not generate at all, leaving bedrock, ocean, and in the Nether and End, skygrids.

In the Xbox One Bedrock port, there is nothing but oceans, bedrock and lava, and at extreme X/Z levels, stripe lands. Curiously, ocean ruin chests seem to spawn at sea level.

The Nintendo Switch port's Far Lands appear in the same way as in the tablet port. However, if players wish to move about this version of the Far Lands, they will need to use a simple trick with the elytra.

The features of the Far Lands in other Bedrock ports remain unknown.

Edge Far Lands
The Edge Far Lands initiate in an extremely similar fashion to the Java Edition's.

Near the Corner Skygrid, terrain may start to become extremely repetitive.

Despite 256 being the maximum buildable height, the Far Lands will still be cut off at y=128, although trees will generate normally.

Nothingness
In the Far Lands with negative X coordinates, after the positive X coordinates degrade, and everywhere in the Windows 10 Edition, terrain will stop generating entirely, resulting in there being nothing present aside from the ocean and the bedrock layer.

Structures can generate here, with some such as desert temples having amusingly elongated foundations. Desert wells, dungeons, abandoned mineshafts, woodland mansions, and fossils cannot generate here.

Strangely, if an igloo generates, it will generate underwater on the bedrock layer, replacing the bottom bedrock layer with stone bricks, and has a magenta bed.

Skygrid
In the Corner Far Lands, far lands with negative Z, and past the normal positive Z Far Lands, an extremely unusual and intimidating grid pattern of grass blocks will appear instead of the ordinary stack/loop. Tall grass and trees will generate on these blocks. This results in a perfect three-dimensional array of grass blocks levitating high above the ocean. Structures generated here follow similar rules to that of the Nothingness.

Stripe Lands
The Stripe Lands are an artifact of the game's rendering, rather than a quirk relating directly to terrain generation. The Stripe Lands starts at X/Z ±16,777,216, under the same terrain effects as Nothingness and Skygrid.

Past ±33,554,432 blocks are rendered as two-dimensional.

Effects
In Bedrock Edition, the playable range is smaller than that of Java Edition, because of the usage of 32-bit floating-point numbers (as opposed to 64-bit on Java Edition). Many of the anomalous terrain-related effects do not occur on the Windows 10 edition, instead just being ocean.


 * Extremely minor jitteriness can be first experienced at X/Z±16,384.
 * Around X/Z: ±32,768, it becomes impossible to sneak diagonally on soul sand which is below cobwebs while drawing back a bow; this effect eventually evolves into being unable to move diagonally at all at far more extreme coordinates.
 * At X/Z: ±524,288, easily visible jitteriness is experienced and the further the player travels, the world gradually starts to become glitchy and unplayable.
 * Past X/Z: ±1,048,576, the jitteriness becomes considerably unbearable, making crashes very frequent at this point on low-end devices. Cacti, levers and some entities are glitched from this point onwards.
 * Past X/Z: ±2,097,152, it becomes impossible to move while sneaking.
 * Just before X/Z: ±1,048,576, and especially after X/Z: ±4,194,304, the blocks' hit detection becomes glitched and can be only hit from behind or in front, as a result; entities less then 1.2 meters wide will fall through. However, it will occur for the player randomly. Horseback and water are the only acceptable ways to travel from here onwards.
 * Beyond X/Z: ±8,388,608, the jitteriness of the player and mobs causes them to fall through the world. However, the player can still continue traveling on horseback though, so "walking" to the Far Lands is possible.
 * FarLandsEdge PocketEdition.jpg terrain erroring initiates at X/Z ±12,550,821 as in Java Edition.
 * Between X: ±12,561,029 and X: ±12,758,546 the Far Lands begin to take on a thinner "shredded" appearance, before fading out into either a Nothingness or Skygrid state.
 * What generates from there to the beginning of the Stripe Lands (X/Z: ±16,777,216) is just ocean, with a floor of bedrock. The bedrock generates in a pattern identical to how it normally generates underground. Biomes will still be there; swamp will darken the water and cold biomes will generate ice on the top layer of the water. Generated structures, such as villages, witch huts, and jungle temples, will still generate here. Large blocks of land will eventually phase out to become long thin strips and eventually dotted arrays of floating blocks resembling a 1-dimensional cross section of the skygrid. On the Z axis, instead of fading out into nothing, the world becomes a skygrid.
 * Beyond X/Z ±33,554,432 water can only be viewed from the side, and becomes non-solid. Only one block face is rendered, thus blocks appear to be two-dimensional.
 * Generated structures like villages and ice spikes may continue to generate as far up to X/Z: ±134,217,728, however they appear two-dimensional at this distance. In the Windows 10 edition there is no limit to how far out structures can generate, and can be seen at distances of over 2 billion blocks.
 * MCPEFarLandsEnd.png every power of two in the Stripe Lands, gaps between rendered blocks increase. At X/Z ±1,073,741,824, blocks stop rendering entirely. The map is invisible from this point onward.
 * Near X/Z: ±2,147,483,647, the game freezes and crashes. However, not all devices are able to reach this point.
 * Blocks that are not full (stairs, fences, etc.) will appear as full blocks, usually stretched out.
 * At very large X/Z coordinates, the player can only move horizontally or vertically unless they sprint-fly, and has to hold down directional keys before moving.
 * Caves generated close to the Far Lands will sometimes have an edgy "zipper" consistency, with sometimes only every second block being hollowed out.
 * Flying is the only ways to navigate the Far Lands. Travelling by foot is impossible as the terrain is made up of ghost chunks.

Dimensions
The Far Lands of the Nether, End, and would-be Sky Dimension share characteristics of the Overworld Far Lands, although with some differences.

The Nether


The Nether Far Lands are similar to the Overworld Far Lands, except generated with Nether terrain features, with a lava ocean at Y=31.

In the Nether, the terrible lag associated with the Overworld Far Lands will not occur; most of the Nether is already dark enough for spawns in the first place, and there are less gravity-affected blocks (no sand, and gravel is rare).

If a nether portal is created in the Far Lands of the Overworld, entering will cause a teleportation to normal Nether, as X/Z 32,000,000, the limit at which block physics and lighting cease to function, divided by 8 (as 1 block in the nether corresponds to 8 blocks in the Overworld), is X/Z 4,000,000, within the limits of X/Z 12,550,820, where the distortion starts. Conversely, a nether portal built in the Nether Far Lands will not function, as even at the limit of 12,550,820 blocks at the beginning of the Far Lands, it would cause the player to come out at X/Z 100,406,560, far past X/Z 32,000,000. If a portal is to entered in beyond X/Z 4,000,000 in the Nether, it will cause the game to crash. Entering a portal at exactly at X/Z: 4,000,000 in the Nether will teleport the player around 8-16 blocks from the 32,000,000 limit.

The Far Lands will not generate above the bedrock ceiling for obvious reasons, even if the Far Lands are modded into a more recent version.

The Nether can be a great way to reach the Far Lands in the Overworld, as every block in the Nether is 8 blocks in the Overworld.

The End
Far Lands have never existed in the End in the desktop version without mods, since the end dimension was added after the removal of the cause of the far lands. Nonetheless, they are available in the Bedrock Edition. They are not of much interest, being made of almost exclusively end stone, and appear a bit more squashed and stretched horizontally than the Overworld lands. Micro-end islands still generate inside the Far Lands, even after they dissipate. Since there is no signature liquid of the End, they just generate down to a dry void; similarly, there is no bedrock floor.

Interestingly, if the Far Lands were modded back into the game before Java Edition 1.9, the End far lands would generate obsidian pillars everywhere on this landmass; end cities and chorus is generated as expected in more recent versions.

The End Far Lands are cut off at y=128, although structures still generate on top.

Sky Dimension
The Sky Dimension similarly has no trademark liquid and will generate no water/lava, and also no bedrock will generate. They appear squashed similarly to those of the End.

The sky dimension far lands will appear just like the End far lands, but with Overworld features.

Cause
The terrain is generated based on 16 octaves of Perlin noise. Each noise generator takes floating-point inputs and uses those to interpolate between noise values at whole numbers. It does so by:


 * 1) Casting to a 32-bit integer, where Java rounds toward zero and handles overflow by picking the closest representable value;
 * 2) Subtracting one if the integer is greater than the original input, to always round down;
 * 3) Subtracting that integer from the original input to get a remainder in the interval [0, 1) suitable for interpolation.

It covers an interval of [−231, 231) without causing any problems. The problem is that many of the octaves cover a scale much smaller than a block, with up to 171.103 noise units per block. Indeed, 231≈171.103×12,550,824.053. Thus, the effects of the Far Lands start 12,550,824 blocks away from the center of the Minecraft world. Once this value is exceeded, the integer will always be 231−1, picking the same noise values on that axis every time. This is the reason for the long unchanging tunnels in the Edge Far Lands, and plains in the Corner Far Lands.

At the positive end the remainder starts out relatively small but usually much larger than 1, and grows by 171.103 per block. At the negative end, the remainder starts at −232. This value is then adjusted by ((6x−15)x+10)x3 for quintic interpolation. Even one block in at the positive end, this is already around 1011. The negative end starts all the way around −1049! For the Corner Far Lands, multiply the values of both edges. When interpolation (really extrapolation) is attempted with values as large as these, it produces similarly large output. That output completely dwarfs all other terms that would normally give the terrain its shape, instead effectively only passing the sign of this one noise function through.

It was fixed by taking the remainder of the input divided by 224. Noise repeats every 28 units anyway, so it has no side effects. However, it does prevent the overflow. By removing these instructions, the Far Lands can be returned to current versions of the game.

There are several other factors to the cause of the Far Lands effects, making things slightly more complicated:


 * Noise is only sampled every four blocks and linearly interpolated in between. This is why when 12,550,824 is affected by the bug, it reaches out three more blocks to 12,550,821.
 * Each noise generator picks a random offset in [0, 256) to add to its input. This will usually move the boundary under 12,550,824, starting the Far Lands at 12,550,821. With a few seeds it might not, putting the start at 12,550,825. Very rarely, if the boundary is just barely within 12,550,824, the first couple blocks of the Far Lands might look somewhat normal. The southern and eastern Far Lands do this independently of one another. At the negative end, the Far Lands always start at block coordinate −12,550,825, with the positive edge of those blocks at −12,550,824.
 * There are actually two sets of noise generators, which are blended together based on another noise generator. This is responsible for relatively smooth alternation between two sets of tunnels or plains. Occasionally, one of the noise generators starts generating the Far Lands before the other because it uses a different offset, producing an incongruous boundary.

Trivia

 * There is a chance of walking into a "bad chunk" that has such corrupt and unreadable data that it will cause huge lag spikes and possibly crash the game.
 * In Release 1.6.2 for 64-bit machines, the limit of how high up you can teleport is +4,599,999,999,999,999 blocks high. Prior to Beta 1.8, you could teleport up to the limit for 64-bit machines.
 * When at the Far Lands, fences either have a thin wall collision box on one side, or no collision with mobs or the player.
 * Even though Beta 1.6 made it impossible to place solid blocks at layer 128, the Far Lands' flat "ceiling" still gets generated there.
 * Because of the debates over renaming endermen to "Far Landers," Notch jokingly suggested to rename the Far Lands to The End instead. This then became the name for the dimension where the Ender Dragon resides.
 * Minecarts with chests will sometimes appear in phantom chunks, but as entities, they fall into the void shortly after they are generated.
 * One of the random splashes reads: "Check out the far lands!". Ironically, the splash was added to the game after the Far Lands were fixed.
 * In Beta 1.7.3 and below:
 * At every power of two after 225, a terrain glitch causes the area around the spawn to generate for a few chunks before generating distorted terrain again. This is the only occurrence where trees generate beyond X/Z: ±32,000,000, the limit at which block physics fail to function correctly and lighting ceases to work. This will continue until X/Z: ±2,147,483,647 (the point where world renderer stops working and surface textures fail to generate).
 * At X/Z: ±2,147,483,519, world renderer stops working completely, ending terrain generation in Minecraft. Things using 32-bit integers will overflow at this distance, causing the game to crash. Chunks will still generate, but there will be nothing inside them other than air. The map will stop generating surface textures past this point.
 * It is very dangerous to reach X/Z ±4,294,967,296 or higher, as the chances of crashing (assuming you have 64-bit Java) are extremely high, and get higher the further you go.
 * In the fourth episode of Minecraft: Story Mode, Jesse and his/her group visit the Far Lands, in which a secret lab is located. The character Ivor describes the Far Lands as "a happy accident", and "nature's way of keeping life interesting". The bizarre terrain is featured and observed by the characters, although understandably, the glitches associated with it aren't present.
 * Horses, Donkeys, Mules, Spiders, and Polar Bears are the only mobs that can stand in the Far Lands.

Video
A user named Booin Muffin has teleported to the 64-bit integer limit: