Example of Cuban military architecture of the 18th century. This is one of the largest Spanish fortresses in the Americas. It was built more than three centuries ago on the western coast of what is now Matanzas Province, to protect the territory's trade and the area east of Havana against attack by corsairs and pirates. Up until 1978, when it was declared a national monument, it served as a prison. Since then, it has housed the Slave Route Museum.