The idea of a space city, the International Space Industrial City (ISIC) is practical. The city has artificial gravity maintained by revolving around a central axis. The rate of rotation depends on the distance of the habitation level from the central axis so to maintain a gravitation force one would normally feel on the surface of the Earth. The energy required to maintain the city comes from thorium reactors as described in the article "The Thorium Question". Details of the city are described there including the propulsion systems to maintain the various momentums of the city.