Barony was the capital city of planet Giedi Prime during the rule of House Harkonnen. After the fall of the Harkonnens, the name of the city was changed to Ysai.
Barony's skyline was dominated by an extremely large rectangular building in its centre, which was surrounded by mostly low-level housing. The structure was 900 stories tall and 45 kilometers long, with no access at ground level, as it was a slave colony. It was here that Duncan Idaho was enslaved with his family. Architecturally, the idea was so that the populace could "look up" to its rulers, and remember their lowly place.
Much of Barony's population was slave labour to operate Harkonnen factories and die as gladiators and sport in the entertainment arenas, usually for the sake of the rich Houses Minor who maintained operations there.
The city was renamed Ysai after the Harkonnens left Giedi Prime and the planet was renamed Gammu. However, the skyline remained largely unchanged.
After The Scattering, The Planetary Bank of Gammu maintained its headquarters at Ysai.