Initially designed by the Italian, Juan Battista Antonelli, the fort was built between 1590 and 1610 to protect the harbour from raiding pirates. It was finally completed in 1700.
In 1622 English privateers took control of Santiago for two weeks, and this helped hasten the repair and completion of the citadel. The fortress has suffered in the past from earthquakes.
This is now a World Heritage Site.
Modern image from CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=314651
1998 image from P. Francis Member of Fortress Study Group.