This UNESCO-listed architectural gem is like a potted history of Portugal's maritime epic. The elegant Manueline tower was built between 1515 and 1519 in the middle of the Tagus (whose course was altered by the earthquake) to defend the mouth of the river and the Hieronymites Monastery. The Romanesque-Gothic structure is adorned with Venetian-style loggias and small domes reminiscent of Morocco, where its architect, Francisco de Arruda, is said to have travelled. It was also used as an arsenal, a prison and a tollbooth for ship taxes.