Belém Tower, also known as the Tower of St. Vincent, is a historic fortress located in the Belém district of Lisbon. Built in the 16th century, it served as a defensive structure and played a significant role in Portugal's maritime history. The tower is a UNESCO World Heritage site and is known for its unique Manueline architectural style. Visitors can explore the various levels of the tower, including the terrace, where they can enjoy panoramic views of the Tagus River and the city of Lisbon.