St. Augustine Castillo de San Marcos#

St. Augustine Castillo de San Marcos, May 2013, © Ewald Judt, under CC BY 4.0

The Castillo de San Marcos 29.897188,-81.312798 is the oldest masonry fort in the continental United States and covers an area of 320 acres (1.29 sq km). The fort was designed by the Spanish engineer Ignacio Daza and construction started in 1672. The construction of the fort was an answer to destructive raids in 1668. It was besieged twice and changed hands six times, all peaceful though. After 251 years of continuous military possession the fort was, following the declaration as a National Monument in 1924, finally deactivated in 1933.