Trantor

Trantor is depicted as the former capital of the First Galactic Empire[?]. Its land surface of 200 million sq. km. was, with the exception of the Imperial Palace, entirely enclosed in artificial domes. It consisted of an enormous megalopolis that stretched deep underground and was home to a population of 40,000,000,000 (40 billion) human inhabitants.

In the earliest stories Asimov placed Trantor in the centre of the galaxy. In later stories he acknowledged the growth in astronomical knowledge by placing it as close to the galactic centre as was compatible with human habitability.

Trantor represents several different aspects of civilisation. At once it is both the centre of power in the Galaxy, and also the administrative head. It is also an illustration of what could eventually happen to any urbanised planet. Asimov used the Roman Empire as the creative basis for the Foundation series, so Trantor is in some sense based on Rome at the height of the Roman Empire. Trantor also illustrates the mentality of human beings that was first encountered in Isaac Asimov's The Caves of Steel, wherein human technology will ultimately result in a complete encapsulation of a population, and that population will eventually suffer psychosis associated with that total encapsulation. Asimov did once say that these encapsulated cities represented the kind of place he'd like to live.

There have been some serious attempts to illustrate a planet like Trantor in the Star Wars films by George Lucas, the first being the Death Star and the other being Coruscant. The Death Star isn't a city as such since it is entirely man-made (it's more like "Roger's Planetoid" in E. E. Smith's Lensman series). Thus, Coruscant is one of the more convincing images on screen we have today of Isaac Asimov's conception of the world-girdling city of Trantor.