Have a look at this unfinished map I have in progress of Escher's 'Impossible Staircase' picture. It's bloody hard to do, and I may start all over. The entire structure has to be much smaller and the staircase sections a perfect sqaure for the illusion to work. Oh well, the first attempt taught me some valuable lessons...
P.s. Yes I know there exists a counter-strike level in the map vault the same as this, but I just wanted to give it a try.
I will also make some other Escher themed maps.