This interpretation centre provides information on what was one of the most emblematic monuments of the history of Pontevedra. Excavations to create an underground car park unearthed some very well-preserved walls, which were part of the defensive moat of the medieval fortress. This discovery led to the construction of a 715 m2 underground museum where visitors can explore the past of the city. The old castle was built in the early 12th century and Ferdinand II donated it soon after, along with the rest of the town, to the archbishopric of Santiago. The fortress was barely affected by the Irmandiño Wars, but it did suffer severe damage from the confrontation between Alonso II de Fonseca, archbishop of Santiago, and Pedro Álvarez de Soutomaior, better known as Pedro Madruga, during the civil war (1474-1477). In the early 18th century, the English set fire to the residence and it was entirely destroyed, with the exception of the impressive keep. It was later used as a prison, until it was decided to completely knock it down in the late 19th century. Additionally, a presentation of approximately 15 minutes is displayed in the museum detailing the function of the city walls.