Generated Structures

Generated Structures are structures or land formations that naturally spawn in Minecraft.

Mineral Veins

 * Mineral Veins are generated structures that contain Ores. They spawn underground and may appear anywhere where there is Stone.

Dungeons

 * Dungeons are underground structures that consist of Mossy Cobblestone, Cobblestone, and a Monster Spawner which can spawn Zombies, Skeletons, or Spiders. They often contain Chests as well, which contain rare and valuable loot.

Villages

 * Villages are above-ground structures with houses, farms, etc. They almost always contain Villagers and rarely, Iron Golems. Villages often have blacksmiths that contain a single Chest filled with useful items. They spawn in Deserts, Savannahs, Ice Plains, Plains or Taiga Biomes.
 * Farmers in Villages can harvest and plant crops.

Abandoned/Zombie Villages

 * They are like regular villages, but with a few exceptions:
 * Instead of Villagers, there are Zombie Villagers.
 * Mossy Cobblestone, Vines, and Cobwebs generate there.
 * There are no Doors.

Desert Wells

 * Desert Wells are naturally generated structures found in Deserts. They carry an infinite source of Water which may be helpful due to Deserts usually containing little to no water sources.

Strongholds

 * Strongholds are underground structures. They are large, having many wings, rooms and halls. They contain the "portal room", the room in which an End Portal is located. This can lead to The End in a future update.
 * There is a Silverfish spawner in there too. They also contain a few chests. They are rarely found under village wells. They also can have multiple massive Libraries that contains one or two Chests.

Lava Pools

 * Lava pools are small pools of Lava that spawn randomly in the world. They are less likely to generate than regular water pools. They are more commonly found in Deserts.
 * Lava pools can set fire to any flammable Block nearby.

Moss Stone Boulders

 * Moss Stone boulders are generated structures that spawn exclusively in Mega Taiga Biomes. They are not rare within the biome, but the biome that they spawn in is rare.

Ice Spikes

 * Ice Spikes are generated structures made completely out of Packed Ice. They only spawn in the Ice Spikes Biome, which are very rare.

Abandoned Mineshafts

 * Abandoned Mineshafts are large mineshafts with randomly generated Rails. They are often connected with Caves. They contain Cave Spider spawners and Cobwebs. Minecarts with Chests can also be found occasionally in Abandoned Mineshafts, with loot inside. They can also spawn in Mesa Biomes as Mesa Mineshafts.

Caves

 * Caves are openings in the surface that lead underground. They often reveal Dungeons, Abandoned Mineshafts, and rarely Strongholds. They also contain ores, Lava, and Water. They can only be found in Infinite Worlds.

Ravines

 * They are large cracks in the Overworld that often lead to various underground structures and rare ores.
 * They aren't currently in Pocket Edition, but may be added in a future update.

Libraries

 * Libraries are structures with Bookshelves present in them. They can only be found in Strongholds and Villages.
 * Village libraries contain, in addition to bookshelves, a Crafting Table, oak stairs/sandstone stairs (used as chairs), and Oak Fences combined with brown Carpets (to serve as tables).
 * Stronghold libraries can be one to two stories high, and contain one Chest per level. The chests can spawn with a random assortment of Books, Paper, Enchanted Books, Compasses, and, as of Update 0.14.0, Empty Maps.

Desert Temples

 * Desert Temples are temples that are found in Deserts, commonly buried with Sand. They have Stained Clay with the loot, as well as a trap below it.
 * The trap contains TNT. The trap is activated when the Player steps onto the Stone Pressure Plate.

Witch Hut

 * Witch Huts only spawn in Swamp Biomes, usually above the water. They consist of Oak Logs, Spruce Planks, spruce Stairs, spruce Fences, and oak fences. Inside is a Crafting Table, Cauldron, and a Flower Pot with a mushroom. Witches can, but do not necessarily, spawn in a Witch Hut.
 * The Cauldron contains a random Potion, which can be gathered with Glass Bottles.

Jungle Temples

 * Jungle Temples are temples located in Jungles. They are mainly comprised of Cobblestone and Mossy Cobblestone.
 * Inside of the temple is a puzzle which requires the Player to flick Levers in a certain order to open up a secret room that contains one of the two chests. The other chest is located in the main room of the temple where Tripwires are set up to shoot Arrows from Dispensers at the Player.

Ocean Monuments

 * Ocean Monuments are structures that spawn underwater in Deep Ocean Biomes. They were added in Update 0.16.0. They mostly comprise of Prismarine, Prismarine Bricks, Dark Prismarine and Sea Lanterns. Inside contains various loot, such as Gold Blocks and Wet Sponges. Guardians and Elder Guardians spawn inside Ocean Monuments.

Glowstone Cluster

 * A naturally spawned structure that is composed of Glowstone. They are found in the ceiling of the Nether Dimension. They are the best way to obtain Glowstone in Survival, with the only other way being killing Witches.

Nether Fortress

 * Colossal fortresses mostly comprised of Nether Brick. They contain chests with valuable loot. Blazes and Wither Skeletons can spawn in Nether Fortresses. They are also the only sources of Nether Wart.

Trivia

 * Before Update 0.11.0, Abandoned Mineshafts contained Spider Spawners, not Cave Spider Spawners. This is because Status Effects didn't exist back then.
 * Before Update 0.9.0, there were no generated structures (except Mineral Veins).
 * Caves, in extreme cases may count as an exception, as they can sometimes generate in pre-0.9.0 seeds such as 'nyan'.
 * Ravines were planned for 0.9.0, but were not implemented.
 * Ravines were also planned for Update 0.14.0, but were not implemented.
 * Bug: In the Google Play Update 0.15.0, sometimes a staircase would be formed in or under the village well. This is due to the failure to spawn Strongholds.