A world in Terraria is divided into five layers that each appear at different depth levels. Each layer has its own characteristics. Most layers contain multiple biomes each.
Space is the topmost layer. It is its own biome and does not contain other biomes. It generally contains no natural structures, although Floating Islands and Living Trees may occasionally extend into it. The Sun, Moon, and stars are visible here against a backdrop that is always black, regardless of the time of day. Gravity is reduced in space, making characters jump higher and fall slower. Harpies spawn here, and in Hardmode, Wyverns.
The surface includes the Forests, Deserts, Corruption, Crimson, Jungle, Snow, and Ocean biomes. Meteorite biomes will usually be found here when they generate. The entrance to the Dungeon is also found here. This layer also usually contains the world's Floating Islands, although these are generally located some distance above the main land mass. A surface Mushroom biome can be seeded here by players, but will never occur naturally.
Terrain blocks usually cover some amount of the lower surface layer, with Dirt Wall behind them. Areas below the actual terrain surface (areas you must dig in order to access) are still considered "surface" if they are above 0 feet. If the usual daytime/nighttime music can be heard while underground, the player is still in the surface layer. Below this layer, the music will change.
The underground layer contains the same biomes as the surface layer. This layer begins at 0 feet extends downward to around -650ft, depending on world size. It has a unique backdrop that depicts dirt with stones set in it, as well as unique theme music.
The cavern layer contains the Underground Snow, Underground Mushroom, and Underground Jungle biomes, which are each located beneath their surface versions. It additionally contains generic cavern features that fill the area between those distinct biomes (see cavern for details on generic cavern features). In Hardmode, the additional Underground Corruption or Underground Crimson, and Underground Hallow, will form. A large section of the Dungeon also extends through this layer.
This layer begins at the -650ft mark, depending on world size, and extends downward to around -3000ft. This layer's backdrop is the same as that of the underground, except the dirt is of a darker hue. It has its own theme music.
Usually this layer begins at the -3000ft mark and expands downward to the bottom of the map. Its backdrop depicts veins of flowing lava. The Underworld is its own biome and does not contain other biomes within it. Lava is abundant here. Any Water that flows into this layer disappears ("evaporates") immediately.
| Game mechanics|
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