A metaroom is the term used for a contiguous area within a C3/DS world, such as the Norn Meso in DS, the C3 Jungle Terrarium, or even C1toDS. A metaroom is composed of a background graphic overlaid with many rooms connected by doors. The rooms define the open space within the metaroom, as well as the contours of the floor, walls and ceiling which creatures and other agents react to. Often metarooms have music files associated with them; individual music tracks may be specified per room, but the music files themselves are usually per metaroom.
Every metaroom in C3/DS occupies a position in the map, although their locations do not necessarily reflect where they "should" go--the Creatures 3 environments are all arranged in a rough rectangle, while the "main" part of the ship is just below them. The placement of third party metarooms is left entirely up to the creator.
The original world map is mostly full, though there are a few gaps for small metarooms. However, the map can be expanded to one hundred times its original area with no known issues, allowing for many more metarooms to be placed. A list of Creatures 3 and Docking Station metaroom coordinates is maintained on the Creatures Wiki.