Built from 1582 by order of Philip II of Spain (Philip I of Portugal, during the Iberian Union) to guard the mouth of the Sado and keep an eye on the town, São Filipe is an Italian-style star fort — one of the best examples of the type in Portugal. The walk up from the old town takes about 15 minutes; five by car.
Inside the walls, the chapel of Santa Bárbara (1714) is clad wall-to-ceiling in blue-and-white azulejos by Policarpo de Oliveira Bernardes — one of the great 18th-century tile painters. The scenes from the saint's life are extraordinary in morning light.
The ramparts open over the city, the bay, the Arrábida ridge, and Tróia across the estuary. Part of the castle was a pousada hotel for decades; today the space is public, with free entry to the courtyard and chapel. A superb sunset spot — the sun drops over the Arrábida.