Stratus City was a city suspended high above planet Kortog. It was the academic and intellectual capital of the Cerullean Sector, and possessed the famed Hall of Knowledge, which was said to hold the secrets of the Great War and the history of both Cragmites and Lombaxes.
Once a great capital city, Stratus City eventually fell under the control of Tachyon's imperial rule. During his occupation of the city, the Hall of Knowledge was put under strict imperial guard to prevent anyone from learning the truth about the Cragmites. Ratchet and Clank landed on this planet after being jettisoned from the Smuggler's ship. It was here that Ratchet fought his way through the city to the Hall of Knowledge, and where Clank got the Robo-Wings from the Zoni. After Tachyon's defeat, Stratus City was presumably moved back to the power of the Galactic President.