The original Fortaleza, also known as the Palacio de Santa Catalina was only one circular tower at the corner of four walls surrounding a large patio.It was completed in 1540 as a defense against Carib indian attacks.Its lack of military value was soon realized and it was used as the residence of the island's governors. It is the oldest executive mansion in the hemisphere still used as such. It has been occupied twice by invaders; by the Earl of Cumberland in 1598 and by the Dutch General Bowdoin Hendrick in 1625 when the building was damaged by fire. A major reconstruction was undertaken in 1640.In 1846, during the reign of Queen Isabel II, the building was remodeled and given a palatial aspect, uniting harmoniously 16th century military architecture with the refinements of the 19th century.
Today La Fortaleza remains the governor's official residence and administrative headquarters. Guided tours are available through the public areas of the mansion including the Hall of Mirrors, used for large formal gatherings, the Informal Dining Room and the Blue room, the governor's formal reception room.