Board Thread:General Discussion/@comment-173.66.124.97-20161016183727/@comment-29966218-20161026155428

There are some undeveloped areas in the game that no one is exactly sure what they're for. They're usually deep, all across the map and blocky. Some speculation includes testing areas, unfinished biomes in early development or abandoned projects that were forgotten.

The deepest biome is the ALZ which is very near the crush depth of a fully upgraded P.R.A.W.N. suit (1700m).