I’m sure you played Nethack.
Of course you remember the annoying level that is a huge open space with a few rooms around the edge? Probably populated by twisted evil dwarves with a deathwish and a serious hate-on for adventurers?
This is the Deep Hall of Druhn in a nutshell.
If you like this map and would like a whole book of maps in a similar vein, as well as adventures and more awesomeness, check out Dyson’s Delves.