Gravity Control Centers were structures on Cloud City in the gas giant Bespin. Six of them were used to regulate the city's gravity, and if disabled, the city could be destroyed. In 3 ABY, the city was attacked by the Galactic Empire to take control of the city after Baron Administrator Lando Calrissian betrayed Darth Vader. The Rebel Alliance defenders attempted to destroy the Gravity Control Generators to prevent the city's takeover.