Inside the castle walls is a peaceful garden, overgrown with tall trees, and the ruined but lovely Gothic Igreja de Nossa Senhora da Penha, originally built in the 12th century and rebuilt by João I in the early 15th century. It has beautiful leaflike carvings over one arch (and don't miss the fascinating marcas de canteiro, unique insignias chiselled on the bricks to indicate which builder laid it and was due payment by the king).
The castle’s most spectacular feature, however, is a gallery with stone seats. It provides a fantastic vantage point over the town’s roofs, though the structure is largely the result of restoration. The castle sits upon a clifftop site that got its first castelo in the time of the Moors; it was captured by Afonso Henriques in 1135. Be sure to climb the recently re-opened tower; it exhibits replicas of medieval costumes, including armour, helmet and swords.