At the fort in St. Augustine. Orb in motion.

The Monument site consists of 20.5 acres and includes a reconstructed section of the walled defense line surrounding the city of St. Augustine incorporating the original city gates. The Castillo de San Marcos' architecture and detail are distinctive and unique. It is the oldest masonry and only extant 17th century fort in North America. As such it is an excellent example of the "bastion system" of fortification.