I've spotted the announcement for another Thief mission design contest, limiting the maximum size of the level
http://www.ttlg.com/forums/showthread.php?t=140798

Then I remembered, that there were hot and very well made constrained levels for Doom... Actually there's a ton of them.
Congestion 1024 http://doomworld.com/idgames/index.php?id=13958
Claustrophobia 1024 http://doomworld.com/idgames/index.php?id=15748
Claustrophobia 1024-2 http://doomworld.com/idgames/index.php?id=15982
Congestion 384 http://doomworld.com/idgames/index.php?id=15600
And the utterly ridiculous Congestion 64 http://doomworld.com/idgames/index.php?id=14009
(the player's character in Doom takes up 32x32 alone)

So, are there any map packs for i.e. Unreal, Quake designed to squeeze decent gameplay in an extremely confined area?