Enable the console window in the game options. Then, press ~ (or `) during game play and enter "map" at the console window.

Now type after that one of the following levels to jump to the corresponding level.

centipede1
centipede2
facade
fortress1
fortress2
funhouse
garden1
garden2
garden3
garden4
grounds1
grounds2
gvillage
hedge1
hedge2
hedge3
jlair1
jlair2
keep
pandemonium
potears1
potears2
potears3
qlair
rchess
skool1
skool2
tower1
tower2
tower3
utemple
wchess1
wchess2
wforest