The Bastion is a tower located in the Imperial City Prison District. The tower stands in the middle of the district.
The Bastion is the lower part of the tower, this is where the Imperial Jailor, evidence chest and the common jail cells are located. There are also 3 doors here, one leading to the back of the Prison District, one leading to the front of the Prison District and one leading to the Imperial Prison itself. There's also a ladder leading up to the Bastion Tower, which is used as a barracks for the Jailors.