The Chao world is where all known Chaos in the world of Sonic Adventure 2 reside. It can be entered by collecting a special key from a "Chao Box" during ordinary levels, which will transport the player directly to the main Chao garden upon the level's completion. It can also be accessed at any time after being unlocked in such manner by going to the Stage Select screen and selecting the Chao icon.

Travelling to the Chao world via the Stage Select screen will output the player to the Chao world lobby instead of the main Chao garden. The Chao world lobby is a small, circular room made of transparent panels and seemingly floating in the void. It has background music which eight-year-old me found very unsettling, but modern me finds quirky, unique, and unsettling.

Attached to the Chao world lobby are doorways to each Chao garden unlocked (Regular, Hero, and Dark), as well as a doorway to the Chao Kindergarten.