Castillo de San Marcos…

The Castillo de San Marcos offers FREE admission on the weekends surrounding National Park Week…
Saturdays–Sundays, April 15, 16, 22, and 23, 2017…. 8:45 a.m. – 5:15 p.m. Last entry is at 4:45 p.m.
Located on the Bayfront in Historic Downtown St. Augustine.
Please call (904) 829-6506 for more details.

The first coquina stones were laid in 1672.  The construction of the current fortress was completed in 1695, it would undergo many alterations and renovations over the centuries.  

Possession of the fort has changed six times, all peaceful, with four different governments: the Spanish Empire, the Kingdom of Great Britain, the Confederate States of America and the United States of America (Spain and the United States had possession two times each).

Photo found on the Library of Congress website.