Discoveries by Portuguese navigators transformed Lisbon into the world’s main trade hub in the 15th and 16th centuries. To protect the city, King João II conceived a pioneer project to defend Lisbon from enemy ships, a work completed in 1514 and which included the building of the Belém Tower, designed by architect Francisco de Arruda. The tower’s unique design includes a modern and heavily armed bastion, protruding over the river. King Manuel I clearly wished the Belém Tower to stand as a lasting symbol of his powerful reign.