This ruined castle, built in the 11C by Ferdinand 1st, who played a major role in the wars against Portugal, was recently converted into a pleasant tourist attraction. Laid out in a lozenge shape and surrounded by a moat, it features three towers. Sculpture by Baltasar Lobo adorns the gardens and castle. The towers and ramparts command fine views of the cathedral's dome and bell tower, the town and the surrounding countryside.