Cave



A cave (also known as a cavern) is a common terrain feature that generates in the Overworld and the Nether. Caves are usually found underground. They are open spaces of various sizes and shapes that often intersect with each another or with different generated structures, creating vast cave systems. They feature an abundance of ores, as well as hostile mobs that spawn in the darkness.

Generation
Caves are underground structures consisting of randomly generated cavities of air, water or lava, hollowing out an area and exposing other blocks generated with the terrain (such as stones and ore features) in the interior. Their structure typically consists of a series of irregular tunnels branching off and winding in other directions, which may connect to the surface, creating natural entrances to the cave. In jungle biomes, vines generate in caves near the surface. Sand often falls into caves generated near the surface of a desert or beach; craters in the sand can alert the player to caves below the surface. Caves cannot cut through red sand nor snow blocks, despite these generating as a surface block in several biomes.

Caves generate at any altitude up to Y-level 256, and may span from the surface all the way to Y-level -59. They frequently intersect natural structures such as other caves, dungeons, ravines, and mineshafts. Because of low light levels, hostile mobs and certain animals like bats and glow squids (only in water) often spawn in caves.

Types
Caves come in two types: carver caves and noise caves.

Carver caves
A cave may have a main room (aka. circular void) connecting 1 to 4 trunks, each trunk with zero or two branches. It may also have no main room, only one trunk and zero or two branches on it, that is, an I-shaped or T-shaped cave. There is a one-in-four probability of generating a cave with the main room, and another three-quarters probability of generating an I-shaped or T-shaped cave.

The main room is an ellipsoidal void of various size. It sometimes may be too small to be found, making the cave looks I-shaped or T-shaped. But as long as the cave is not I-shaped or T-shaped, it must have a main room.

For each trunk or branch, it is usually thin at both ends and thick in the middle. However, the thickness does not vary so evenly. It sometimes flickers thick and thin as it advances. Sometimes it becomes so thin that there are some interruptions. Multiple interruptions make it look like a series of continuous bubbles. The length from the root of the trunk to the top of a branch varies from 85 to 112 blocks.

The trunk and branches are curved, and they are often intertwined with each other, making the cave very complex. Multiple caves sometimes merge with each other making them more messy and spacious.

The ceiling of the main room, trunks and branches is usually round, while the floor usually tends to be flat.

Overworld cave
The cave generation in the Overworld starts from Y=-56 to Y=180. The probability of cave generation is higher at Y=-56—47.

Their main rooms vary from roughly 1 to 14 blocks in height, and from roughly 5 to 15 blocks in diameter.

The horizon thickness of trunks varies from roughly 2 to 38, while the vertical thickness of trunks varies from roughly 1 to 36.

The horizon thickness of branches varies from roughly 2 to 7, while the vertical thickness of trunks varies from roughly 1 to 7.

A cave may connect to the surface of the terrain, creating natural entrances to the cave. They sometimes connect to the sea. Caves also regularly contain at least minor water or lava flows as well as a number of aquifer of water and lava.

Nether cave
The cave generation in the Nether starts from Y=0 to Y=126.

Their main rooms vary from roughly 2 to 8 blocks in height, and from roughly 5 to 15 blocks in diameter. Compared with the caves in the Overworld, the vertical thickness of the caves in the Nether is higher. The horizon thickness of trunks varies from roughly 3 to 15, while the vertical thickness of trunks varies from roughly 12 to 64. The horizon thickness of branches varies from roughly 3 to 5, while the vertical thickness of trunks varies from roughly 12 to 22.

Underwater caves


Underwater caves are completely flooded caves that may have underwater magma.

Being completely underwater, only the magma blocks provide any air for entities to breathe, since they generate bubble columns. They have sometimes seagrass, but since they don't generate exposed to sky kelp cannot generate, unlike sea-access caves.

Noise caves
Noise caves are generated using a noise. They come in the form of cheese caves, spaghetti caves, and noodle caves. By adjusting noise frequency, hollowness (for cheese caves), and thickness (for spaghetti caves, noodle caves, and noise pillars), noise caves can vary in extremely diverse ways. When generating noise caves, the game firstly generates a random noise field, and "smudges" it using a mathematical trick called Perlin noise. These processes then result in a 3D noise image. Noise pillars also generate inside cave blobs.

Cheese cave


Cheese caves are pocket areas of the underground that come in various sizes. Cheese caves offer large and open spaces, being the largest cave type on the game. They frequently generate noise pillars and expose many ores. When generating, the black part of noise image becomes stone or deepslate, and white part becomes air, making it resemble a cheese with many holes.

Spaghetti cave


Spaghetti caves are long, narrow caves that wind their way through the underground and are a bit similar to small or medium carver caves, but longer. When generating, the edge of black and white part of noise image becomes air, making it look like long and wide spaghetti.

Noodle cave
Noodle caves are a thinner and squigglier variant of spaghetti caves. They consist of tunnels usually 1 to 5 blocks in width. When generating, the edge of black and white part of noise image becomes air, making it look like long and thin noodles.

Noise pillar


Noise pillars look like large dripstones or speleothems, but consist usually of stone. They can be found in any type of noise cave, making caves more realistic.

Aquifer
Aquifers are liquid systems used to generate bodies of liquids in a world. Almost all liquids in a world (including those in carvers, noise caves, rivers and oceans) are generated by aquifer. Aquifers may create underground liquid bodies that look like lakes, as well as water or lava waterfalls. Note that lava lakes are also generated underground, but they're not aquifers.

Aquifers below Y=0 may sometimes generate with lava instead of water. And aquifers from y=-55 to -63 always consist of lava, which are called lava oceans.

If two liquid bodies of different levels or types are too close, some blocks may be generated between them to separate them.

Dungeon
Dungeons, also referred to as monster rooms in their ID, are structure-like features that appear in the underground that contain monster spawners. Dungeons are small rooms made of cobblestone and mossy cobblestone and contain a monster spawner and up to 2 chests. Finding a dungeon without a chest is unlikely but possible.

Ancient City
An ancient city is a palatial structure found in the deep dark, harboring chests containing items that cannot be found anywhere else or that help a player avoid a warden. An ancient city features a very large palace that stretches throughout a deep dark biome. The palace is made up of long corridors with gray wool floors to prevent vibrations as well as some smaller ruins off to the side of the main corridors, which contain between one or two loot chests. The city center features a frame resembling a warden's head, where there are reinforced deepslate blocks, which is an unobtainable material in Survival mode. Other unique blocks such as soul lanterns and candles as well as different forms of deepslate can be found here.

Mineshaft
A mineshaft is a generated structure found underground or underwater, having mazes of tunnels with cave spiders and ores exposed on the walls or floor regularly.

Lava lake


Lava lakes may generated underground with air pocket, which makes them look like small caves with lava aquifer.

Amethyst geode
An amethyst geode is a feature found in the underground of the Overworld. Amethyst geodes contain smooth basalt, calcite, and are the only source of amethyst items and blocks.

Cave biomes
There're some biomes generated only in caves.

Dripstone Caves
A dripstone cave is an underground Overworld biome which is often found far away from oceans, in areas with high continentalness values. It features a landscape filled with stalagmites and stalactites, as well as giant versions of them, as well as dripstone block littering the ground. Small sources of water can be found on the floor. Drowned can spawn here in aquifers.

Lush Caves
A lush cave is an underground Overworld biome that is usually found below biomes with high humidity values. It is filled with unique flora, cave vines covering the roof, and clay pools of water on the bottom. This biome can be found underground below azalea trees. axolotls, glow squids, and tropical fish can spawn here.

Deep Dark
The deep dark is an Overworld biome that generates deep underground (below Y = 0), usually in mountainous areas with low erosion values, and never below an ocean. The floor in this biome often has patches of sculk blocks surrounded by sculk veins, which include sculk-related blocks such as sculk shriekers, sculk sensors, and sculk catalysts. No mobs spawn in this biome, but if a player triggers the sculk shriekers a certain amount of times, the warden may appear, giving the player the Darkness effect.

Trivia

 * Before they were added to Minecraft, large underground lakes were already present in Minicraft.