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

A lone gunner's station is all that remains of a replica Spanish Fort in Florida.

These crumbling foundations are all that remain of the once-stately 1840s manor that gave the town of Bradenton its name.

Located within a historic park, the beacon is the oldest standing structure in Miami.

The abandoned bathhouse is all that remains of the hot springs considered Florida's original tourist attraction.

A tribute to Ponce de Leon's supposed quest for eternal youth.

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

Arrr! The most authentic collection of pirate artifacts in the world... matey.

Florida might be at its most surreal in this museum devoted to the famed Spanish artist.

The lowest point in the state of Illinois, at the confluence of the Mississippi and Ohio rivers.

These pretty kitties killed and ate as many as 135 railway workers.

An early-19th-century hotel with a past that is steeped in the Civil War.

A psychedelic tribute to one of Georgia's most unique artistic visionaries, out of place and time in the heart of Atlanta.

One of corporate America's best-kept secrets is also one of the most publicly displayed.

The birthplace of the Ford Model T is now a museum full of antique cars.

Chicago's Navy Pier on Lake Michigan was a training hub for aircraft carrier pilots during WWII.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

This national park on the shore of Lake Michigan features remarkable dunes that lie at the heart of a Chippewa legend.

This former maximum-security prison is creepy, sobering, and supposedly haunted.

The bad-ass ride of a soul legend, housed in one of the world's few soul museums.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

A 90-year-old underground water reservoir offers a more industrial kind of tranquility.

After serving in Vietnam, Korea, and even a stint in the Turkish navy, the unique ship is now open as a museum.