Stronghold



Strongholds are structures that occur naturally underground. They contain multiple rooms, corridors, stairs, doors and other aspects. Strongholds also contain a portal room with an unactivated End Portal, which when activated with twelve Eyes of Ender can be used to travel to The End. Strongholds can be located with the Eyes of Ender.

Appearance


Strongholds vary in size. They are labyrinthine and contain several doors and rooms made mostly of Stone Brick, Mossy Stone Brick, and Cracked Stone Brick. Some treasures found in strongholds include Paper, Redstone, Books, Enchanted Books, Coal, Gold Ingots, Iron Ingots, Compasses, Red Apples, Golden Apples, Ender Pearls, Iron Chestplates, Iron Boots, Iron Pickaxes, Iron Helmets, Maps, Iron Swords, Obsidian, and Diamonds.

Strongholds are primarily generated underground, often unexposed to the surface and only visible within caves, possibly even underwater caves. In some seeds they may be connected to a dungeon or even merge into an abandoned mine shaft. The terrain generator is apparently incapable of discriminating between strongholds and standard blocks, as map generation features such as Underground Ravines and Abandoned Mine Shafts cut indiscriminately through strongholds, often making the strongholds difficult to navigate. It is unclear whether this functionality is intended or not. Strongholds are vacant except for regular mobs that spawn under normal conditions. Strongholds are where Silverfish can spawn, created when someone either mines one of the blocks within, or finds the end portal room, which contains a silverfish spawner. No new mobs besides these have been added to strongholds as of yet.

The majority of a stronghold is composed of many random hallways, pillars, spiral staircases and regular stairways formed with stone slabs. There are both wooden and iron doors throughout the structure, the iron ones operated by nearby buttons. Since all doors seem to generate facing the same cardinal direction, some are initially open, which can lead to the unusual case of an open iron door which closes briefly when the nearby button is pressed. There are decorative arches built out of iron bars placed along the hallways, and random dead ends at blank walls made of regular stone. Torches and chests are scattered around.



Rooms within the Stronghold
Strongholds feature various types of main rooms, such as Prison Cells, Libraries, Storage Rooms, and rooms which function as an intersection with a central fountain or column with torches mounted. There are also unusual rooms with a staircase descending under an arch or bridge against the wall, with another staircase to one side leading up onto this bridge (which rarely allows you to reach anywhere else). While the overall placement and number of these features in the stronghold is completely at random, the features themselves seem to always take the same forms.


 * Prison cells seem to be generated in pairs in the wall of a hallway and feature iron doors without buttons, and are empty, although they may have been used years ago when an older civilization imprisoned various hostile mobs, such as Skeletons and Creepers. The doors are always open.


 * Storage rooms are generated off the sides of hallways. They are empty, contrary to what one may think.


 * Libraries have two sizes: small libraries and large libraries. Small libraries often contain Bookshelves, Wooden Planks, and a chest(s). Large libraries contain more Bookshelves, Fences, Wooden Planks, and torches arranged in an upper balcony with a chandelier over the small library, connected by ladders on the far wall from the entrance. Despite the fixed arrangement of the libraries themselves, cobwebs seem to be placed randomly within.
 * Chests can be found on the corner of bookshelves, and on the upper floor of library rooms. They can also be found on the upper floor of 4-way intersections. Chests in libraries may contain paper, books, and/or a compass, and sometimes a map. Intersection chests may contain coal, bread, redstone, iron ingots, Iron Swords, Iron Pickaxes, armor, Ender pearls, diamonds and/or Red Apples; sometimes chests may contain a very rare item, such as a saddle or a Golden Apple.


 * Every stronghold has an end portal room, with an end portal and a silverfish spawner

Spawning
All Strongholds are located at random in a radius between 640 and 1152 blocks from the origin, 0/0. Due to the generation algorithm, the Stronghold may extend further in or out of that circle. The three strongholds are spawned at roughly equal angles from the center point of the world (that is, each stronghold is in the region of 120 degrees from the others, measured from the origin.). The game will not generate a stronghold partially above-ground: the portion above the ground layer will be replaced with air blocks, leaving a cutaway. There is a limit of 3 strongholds per world.

Strongholds are very often broken by caves, ravines, and Abandoned Mine Shafts. This means that navigating the stronghold can sometimes be very difficult. It also means that it's easy to mine around your home if you decide to live in a stronghold.

Use as a base
Because of their great size, strongholds would seem to be a good place to convert into your base. However there are some advantages and disadvantages.

Advantages

 * In SMP, strongholds are difficult for griefers to find.
 * There is lots of space to fill the stronghold with chests
 * There is the possibility of valuable loot in the chests found throughout strongholds.
 * Because strongholds are underground, it's easy to enter an abandoned mineshaft or large cave system and find valuable ore, such as iron and diamond.
 * The End Portal is nearby so that you do not have to go looking for one.
 * If you become lost above ground, you can find your house using an Eye of Ender

Disadvantages
NOTE: An easy way to detect silverfish blocks is to mine the walls with your bare hands. If it mines quickly, it is a silverfish block.(it takes 1.13 seconds to mine a silverfish block, 7.5 secs to mine stone, and 10 seconds to mine cobblestone/stone brick/etc. this also works if you have a fast pickaxe such as a diamond one, as it takes significantly longer to mine Silverfish blocks than it does to mine most other things.)
 * In SMP people might be looking for Strongholds because of the End Portals and therefore find your base.
 * Mining the walls of a stronghold can awaken silverfish, given the presence of silverfish blocks.
 * Strongholds are often split in half by ravines, abandoned mineshafts, and caves, making living difficult unless completely restored.
 * Since the Strongholds usually intersect with ravines or mines, it makes it easier for PVP players that are mining to find your base.
 * You'll either need lots of torches to ensure no mobs spawn in the stronghold, or be constantly alert and ready for a fight.

Bugs

 * Often when a stronghold overlaps with another underground structure torches or iron/wooden doors will generate floating. If it is an iron door, one can fix it by hitting the button next to the door, which will cause a redstone current to be sent to the door, causing the door to do a block update (in this case, opening) which will make it realize that it's floating and it will destroy itself. The same can be done with wooden doors, but no button is needed.
 * Often when torches in Strongholds (and Abandoned Mine Shafts) generate, they emit no light, but the torch itself is bright.
 * Occasionally, a torch may generate floating in a hallway, also emitting no light, as mentioned above.
 * Doors generate facing the same way, causing some to appear open due to being generated facing the wrong direction.
 * On very rare events, if a stronghold is generated in a ravine, the ladders of the library will float. These ladders can still be climbed, though they are invisible from the other side.
 * Rarely when you throw an Eye of Ender, it will lead you to a random part of a stronghold.

Trivia

 * End portals may become useless or even completely disappear if there is an Abandoned Mine Shaft or a Ravine cutting through it.
 * Due to the way the overground generates, empty blocks replace any part of a stronghold that exceeds the predetermined ground level, thus making a cross section similar to that seen in the first screenshot.
 * Ravines may cut across strongholds, making navigation difficult.
 * Of all the Stone Brick blocks in a stronghold, approximately 45% are regular stone brick, 30% are mossy stone brick, 20% are cracked stone brick, and 5% are actually Monster Egg blocks.
 * While strongholds are usually quite large, sometimes they can be generated with only a few rooms. An example can be found with seed -6195449077980173317 at -850, 20, -200.
 * Be aware that strongholds frequently spawn underwater, which makes reaching them no easy task.