The Fortaleza de Santa Catarina sits on the headland at the eastern end of Praia da Rocha, where the Arade River meets the Atlantic. Built in the 1620s to defend the harbour at Portimão from pirate raids, it is small as Algarve forts go but commands the best viewpoint in town — the long sweep of Praia da Rocha to the west, the river mouth and Ferragudo to the east.
The walls themselves are free to walk and contain a small chapel. A cafe-restaurant occupies the inner courtyard and is one of the better spots in town for a sunset drink. The fort is at the end of the clifftop promenade, an easy walk from the main strip of hotels.