Vodka's fortress is Vodka's main residence that is located in East District. Goku goes here during the Cell Games Saga, to take the Four-Star and the Seven-Star Dragon Balls from Vodka and Cyborg Tao.
The entrance is a hallway covered with holes on the walls, and arrows will be shot from those walls if activated. There was a protective shield around Vodka's office which was easily destroyed by Goku.
In the video game Dragon Ball Z: The Legacy of Goku II, Vodka's fortress is the location of the Four-Star Ball only (the Seven-Star Ball being in the Tropical Islands). It is protected by a Ninja Clan, a Mercenary Clan, ladybugs, Eggbots, a Green Destroyer, and Cyborg Tao.