The Imperial City of Alderaan was the capital of the New Galactic Empire.
It was a vast, platter shaped construct which floated amongst the clouds of the gas giant Alderaan.
It was the home of the Galactic Emperor, the Supreme Tribunal and of the Master of the Sith. Security perimeters surrounded it into deep space.
Inside the Imperial City
Triple guards, scramble scanners, gas locks and the isolation of each sector of the city helped to preserve its reputation of invulnerability.
After being captured above the planet Utapau, Deak Starkiller was tortured and imprisoned in the Imperial City. He was released by Han Solo, Chewbacca, , Luke Starkiller and the droids Artoo and Threepio after they sneaked inside by convincing the Imperial TIE fighter patrols that they were adrift space junk.
Places in the city included the Plaza of the Daders and a .
The bowels of the Imperial City were infested with Dai Nogas, deliberately introduced by the Sith as a security measure.
The look of the Imperial City was designed by Ralph McQuarrie for the second draft. It was re-used for Cloud City in Episode V. The Imperial City was deleted from the draft scripts to Episode IV in the fourth draft.
Lucas, prior to the realization of Cloud City, described a similar environment for "Crell" and mentioned Granicus, the name Alderaan was known as in the first draft, in notes for licensees written in 1977.