Overworld Surface Structures
Structures found on the surface of the Overworld, from villages to pyramids and mansions.
A tent of white wool stairs with a campsite next to it
Sandstone pyramid with orange terracotta
Snow block dome structure
Cobblestone and mossy cobblestone construction
Tall watchtower structure
Incomplete nether portal frame
Contains houses, farms, and workstations
Small wooden hut on stilts
Massive three-story wooden structure
What each surface structure gives you
Eight structures generate on the surface. Most of them deserve a short detour, and a woodland mansion deserves a long one.
Village
Beds, food, a bell and villagers to trade with. The buildings follow the biome, with plains, desert, savanna, taiga and snowy versions. About one village in fifty generates abandoned, with zombie villagers and cobwebs instead of traders. In Java there is roughly an even chance of a village within 500 blocks of spawn.
Pillager Outpost
A watchtower with pillagers spawning around it, sometimes with cages that hold an allay or an iron golem. The outpost captain drops an Ominous Bottle. Drinking it gives Bad Omen, which starts a raid when you walk into a village and makes trial chambers harder. The chest on the top floor can hold the Sentry trim template.
Witch Hut
A small hut on stilts in a swamp. It generates with a witch and a black cat inside, and after that witches are the only mob that can spawn in its area, as long as the whole hut sits inside the swamp biome. That is why witch farms get built around them. In Java the cauldron is empty; in Bedrock it holds a random potion.
Desert Pyramid
Four chests wait in a hidden room under the blue terracotta block in the middle of the floor, and a stone pressure plate down there is wired to nine TNT. Dig down beside the blue block instead of through it, and break the plate before you step anywhere. Each pyramid also has a buried side room with six to eight suspicious sand blocks to brush, and the chests can hold the Dune trim template.
Jungle Pyramid
Two chests. One sits at the end of a hallway with two tripwires hidden behind vines, each wired to a dispenser loaded with arrows; cut the wire with shears and nothing fires. The other appears when you set the three levers on the bottom floor to the right combination, which pulls a block on the main floor away. Both can hold the Wild trim template.
Woodland Mansion
Rare, usually far from spawn, and only in dark forests and pale gardens. Vindicators and evokers guard it, and some rooms hold caged allays. Evokers are one of the few sources of the Totem of Undying, and the chests can hold the Vex trim template.
Igloo
Half of all igloos have a basement. Break the third carpet from the door to find an oak trapdoor and a long ladder. Down there is a brewing stand with a Splash Potion of Weakness, a chest with a golden apple, and a villager and a zombie villager in cells: everything you need to cure a zombie villager. Some of the stone bricks are infested with silverfish, so leave the walls alone.
Ruined Portal
A broken Nether portal next to a chest with gold gear, obsidian and flint and steel. Some frames contain crying obsidian, which cannot be part of a working portal, so swap it for normal obsidian before you light it.
Finding them
/locate structure needs the exact ID, and villages have one per type: minecraft:village_plains, village_desert, village_savanna, village_taiga and village_snowy. The rest are minecraft:pillager_outpost, minecraft:swamp_hut, minecraft:desert_pyramid, minecraft:jungle_pyramid, minecraft:mansion, minecraft:igloo and minecraft:ruined_portal. Ruined portals in deserts, jungles, swamps, mountains and oceans have their own IDs, such as minecraft:ruined_portal_desert.
Without cheats, a cartographer villager can sell you a woodland explorer map, though it does not always point to the nearest mansion. The /locate command page explains the rest of the syntax.