The Torre de Belém (Belem Tower) is undoubtedly Lisbon's most iconic landmark. The tower was built in the sixteenth century in the Tagus river to control the entrance to the city from the sea.The idea to build a fortress near Belém was launched in the fifteenth century by king John II, who commissioned the construction of a tower in the river Tagus as part of a larger defensive bulwark. By the time plans for the tower were completed the king had died and the project was shelved.The project was revived in 1514, during the reign of his successor, king Manuel I. A new design for the fortified tower was created by Francisco de Arruda and construction started the following year near the harbor of Belém, the starting point of many of the Portuguese explorers during the Age of Discoveries. The tower was completed just six years later, in 1521. At the time the tower was known as the Torre de São Vicente (Tower of St. Vincent) as the king had put the tower under the protection of St. Vincent, Lisbon's patron saint.