Colobot Wiki
You are able to download and install custom content created by the community, such as level chapters. Prior to February 27, 2019, users went to the Colobot forum to discuss the game and share content.

Creating levels[]

Colobot has an old manual describing how to create levels.

The ModDB has a level which can be used to test terrain height, and shows every object currently in the game, as well as terrain heightmap examples.