Castillo San Cristobal, San Juan

Last Saturday, the lovely Robin and I had a great time touring the  majestic and imposing Castillo San Cristobal in Old San Juan, Puerto Rico.
The sprawling fortress was built over a period of 150 years by the Spanish to protect the port and city from attack, thus preserving the lucrative plunder of gold and other exports from the New World.
Built on a hill originally known as the Cerro de la Horca or the Cerro del Quemadero, San Cristobal is the largest European fortification in the Americas. When it was finished in 1783, it covered about twenty-seven acres. It is not only an impressive and imposing sight; it also discloses many of the techniques and tactics of sixteenth, seventeenth, and eighteenth-century warfare.
Among the notable features of San Cristobal are the many guerites, or sentry boxes. One of these, below, is known as "the devil's box," or "La Garita del Diablo." Various legends claim that soldiers regularly disappeared from this particular guerite, though local stories tell only of one soldier named Sanchez, who fled his post to escape with his girlfriend. The Devil's Box is inaccessible to visitors; it can only be seen from a distance.

One of the casemates in the fortress is furnished so visitors can see how the troops lived during much of the fort's operational life.
Castillo San Cristobal continued to be used for military purposes through World War II, when various vantage points were fortified and used as lookout posts. Below is the view from one of those. I might have volunteered for that duty.
Perhaps most remarkably, San Cristobal is only one of two major fortifications in the system that protected San Juan until sections were destroyed in 1897 to make room for the city's expansion.