In this case, 'zero' marks the spot where the iconic Old Spanish Trail ends.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

The ruins of a once-thriving sugarcane plantation that was burned in the Second Seminole War.

The ruins of this antebellum sugar plantation are the end result of a Seminole attack during the Florida Wars of 1836.

A replica of one of the more than 15,000 civilian lookout towers that lined the U.S. coast during World War II.

A Prada store in the West Texas desert that is never open for business.

The remnants of the fortress that saved Georgia from the Spanish still stand guard on their swampy island.