Torre del Oro (Tower of Gold) in Sevilla is a military watchtower located on the Guadalquivir River. It was constructed during the 13th century by the Almohad dynasty to control the access into the city and at a point during the Middle Ages, it was also used as a prison.
During the Lisbon earthquake in 1755, the tower was damaged and its demolition was proposed, but the citizens protested and saved it.
The tower has three levels in total. Today, the first two levels are used as a museum featuring navigational instruments as well as nautical charts, documents and more.
Legend has it that the tower was used to store the gold brought from the Americas, however, this story is false. However, according to some sources, King Pedro I did keep treasures hidden in the tower as well as well as Aldonza Coronel, who he fell in love with and took her from the convent she lived in and later on put her in the tower under guard.