Belém Tower (Portuguese: Torre de Belém , pronounced: [ˈtoʁ(ɨ) dɨ bɨˈlɐ̃ȷ̃] ) or the Tower of St Vincent [1] is a fortified tower located in the civil parish of Santa Maria de Belém in the municipality of Lisbon , Portugal . It is a UNESCO World Heritage Site (along with the nearby Jerónimos Monastery ) [2] because of the significant role it played in the Portuguese maritime discoveries of the era of the Age of Discoveries . [3] The tower was commissioned by King John II to be part of a defense system at the mouth of the Tagus river and a ceremonial gateway to Lisbon. [3] The tower was built in the early 16th century and is a prominent example of the Portuguese Manueline style, [4] but it also incorporates hints of other architectural styles. [5] The structure was built from lioz limestone and is composed of a ba...