What is "trantor"

Trantor is a fictional planet in Isaac Asimov's Foundation Series and Empire series of science fiction novels.

Trantor was first mentioned in Asimov's short story, "Black Friar of the Flame", later collected in The Early Asimov, Volume 1. It was described as a human-settled planet in the part of the galaxy not ruled by an intelligent reptilian race (later defeated). Later, Trantor gained prominence when the 1940s Foundation series first appeared in print (in the form of short stories). Asimov described Trantor as being in the centre of the galaxy. In later stories he acknowledged the growth in astronomical knowledge by retconning its position to be as close to the galactic centre as was compatible with human habitability. The first time it was acknowledged in novel form was in Pebble in the Sky.