The fort has guarded the Tagus River since the 16th-century and remains a landmark of Portugese identity.
Under orders from King Joao I, the Belém Tower was built between 1514 and 1519 to defend Lisbon. In the centuries that followed it was transformed into a lighthouse, a prison and a customs centre.
The tower was built from blocks of Lioz limestone which were offcuts from the Jerónimos Monastery; also under construction at the time. The Manueline style incorporates details paying tribute to the Age of Discovery, including stonework motifs, sculptures of historical figures, Arabic style watchtowers, and a unique gargoyle in the shape of a rhinoceros. The tower has five floors which lead to a roof terrace, each storey connected by a narrow spiral staircase.