The Villa was a groundbreaking real-time multi-user dungeon delivered via the telephone creating an audible virtual environment where people could “move” around and interact just by typing on the phone’s keypad (DTMF). The system was running from 1994 to 2001 when the project ended.
The code has been rewritten by one of the original authors and a new system called Alphaville has been created that is now attached to the 22C3’s phone network. Just dial 98 to get in. This time, the virtual space is modelled after the 22C3 building. Check out the description on the wiki for additional instructions.