Überstadt is a homebrew devised by /tg/ around February 2008 that ran out of steam a month later. The idea came into being during a thread about 'reinventing the wheel' with D&D, coming up with new stereotypes for races and classes and whatnot. Most of the information about it is stored on Wikispaces.
Based upon the 3.x D&D system, can be converted to any system you like if you can be arsed.
Überstadt is the name of the greatest city ever to be seen on any of the Planes. Some claim that it even dwarfs Sigil, the City of Doors. No one truly knows how Überstadt was constructed and there are a thousand theories behind its arcane creation, none of them yet verified. The only fact behind the history of Überstadt's creation is that through unknown means, it drew together all of the races of the world, some of them willing, some of them forced and created one of the greatest civilizations in the Multiverse. A place of magic and technology, Überstadt extends from deep beneath the earth to high above the clouds, covering an area of land that it dwarfs small countries. This is the city where the lowly and hunted have become the rich and famous. This is the city where the wise and powerful have become the humble and weak. This is the city that reinvented the wheel.