Belém Tower is a fortified tower located in the Belém district of Lisbon, Portugal. It is an UNESCO World Heritage Site (along with the nearby Jerónimos Monastery) because of the significant role it played in the Portuguese maritime discoveries of the era of the Age of Discoveries. The tower was commissioned by King John II to be both part of a defense system at the mouth of the Tagus River and a ceremonial gateway to Lisbon.

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