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ITERDEAMBULATIO.bsp or just ITERDEAMBULATIO was a server & map that popped up on Half-Life 2 Deathmatch around 2006. ITERDEAMBULATIO would cycle between 5 maps on weekdays, all being called ITERDEAMBULATIO.bsp. On weekends, it woukd stay on one map. you can probably guess the name... The maps consisted of winding concrete hallways with random props. Sometimes there would be triggers that activated point_servercommand entities. After about a year of running nonstop, the server went down. The only map that is still viewable online is version six, AKA the weekend map. I have attatched a video of it.
You can view it here