@gruber I reckon the “weird” space was an artifact of Marathon’s pseudo 3D rendering engine. Which is all the more fascinating.

It was used for effect in at least one of the official multiplayer maps, but not the campaign that I recall.

Did you ever use the map editor? It was finicky and crash prone, but you could make your own maps. The spaces in the game were drawn with vector like points. Creating overlapping spaces was quite tricky, but getting it to work was delightful!