Mineshaft

Mineshafts are common underground structures primarily found underground in the Overworld. They consist of interlinked 3×3 tunnels with incomplete rail lines running through them, with oak planks platforms bridging gaps or hanging in larger exposed caverns.

A unique variant of mineshafts made out of dark oak wood can generate on the surface in badlands biomes.

Mineshafts generate underground in any Overworld biome except for the deep dark (although a mineshaft can overlap). They generate before chunk features such as ores. Multiple mineshafts can generate near each other, producing larger complexes. When mineshafts intersect with caves and canyons, corridors generate a bridge of planks over empty space, either suspended with iron chains above or supported by log pillars below. When a mineshaft intersects with an aquifer, a barrier of solid blocks generates to prevent fluids from flowing into the mineshaft, often resulting in corridors cut off from the rest of the mineshaft.[1]