The Castle of São João da Foz was built during the period of Spanish rule to protect the coast and access to the River Douro; it was later used, during the Siege of Porto (1832-33), for unloading and storage purposes. A renovated old church and asylum belonging to the Santo Tirso Benedictine monks were integrated into the castle. Close by, at the mouth of the Douro, is Portugal’s oldest lighthouse and the adjacent beach is a very popular bathing resort.