The doors are the weakest parts of the walls. In order to protect them, defensive towers were built on their sides. The clearest example we find in Segorbe is the Prison Tower, located next to one of the old city’s gateway, the Portal of Teruel.
Externally, the tower is cylindrical with a lower body of larger diameter and, probably, more primitive than the former, in which the cells used as prisons are located. The second body has a diameter of 8,70m and it is internally divided into two-story octagonal sections, with cross Gothic vaults, arrowslits and communication to the terrace by a spiral staircase embedded in the wall. Its total height is 21,30m. As well as the nearby Executioner’s Tower, the Prison Tower could be dated around the 14th century.