Kalgan

From Asimov

Kalgan is a fictional planet in Isaac Asimov's Foundation Series.  It appears in Part 2 of Foundation and Empire and Parts 1 and 2 of Second Foundation.

In the Foundation Series, Kalgan is a resort world that suddenly finds itself thrust into the center of interstellar affairs in 310 F.E. when The Mule uses his emotional control to Convert its Warlord into his follower.  The Mule makes Kalgan the capital of his growing empire, which he calls the Union of Worlds. At its height, the empire ruled from Kalgan includes one third of the worlds in the Galaxy, including the former Galactic capital world of Trantor and the worlds of the First Foundation.  After the Mule's death, most of the worlds he ruled, including those of the First Foundation, break away, and by the time Lord Stettin becomes First Citizen of Kalgan in 376 F.E. the Union of Worlds includes only 27 planets.  Following defeat by the First Foundation in 377 F.E., Kalgan's subject worlds are made autonomous and offered the choice of returning to Kalganian rule, becoming independent, or joining the First Foundation. Kalgan plays no further role in Galactic history.