The Fort of St. Vincent (Belém Tower) lies in the Tagus River in Lisbon. It was built in the early 16th century to fortify the Portuguese capital city's defenses against a seaborn invasion. However, despite being later strengthened, the tower surrendered to Spanish forces after just a few hours of battle. It was subsequently used for a prison. After falling into a state of disrepair, the tower was fully renovated in the 1990's. It is now listed as one of the Seven Wonders of Portugal.