An 18th-century Spanish watchtower made entirely of seashell and concrete.

The famous Beatle secretly visited this Illinois town several times to visit his sister.

A sprawling outdoor museum filled with larger-than-life works of art.

A historic and oft-filmed prison stands in a Chicago suburb.

This national park dedicated to the tallgrass prairie ecosystem still displays its military past.

Ruins of an old sugar mill sitting quietly next to a park in rural Florida.

In Florida, these naughty monkeys live on their own mini-monkey Alcatraz.

Public works and national defense project meant to carve a canal all the way across the state of Florida.

Meet manatees face-to-face at this zoo for native species.

A Florida college boasts the world's largest single-site collection of structures designed by Frank Lloyd Wright.

A haunted hill that supposedly defied gravity.

A secret, rocky playground hidden amongst the plain white beaches of the Florida coast.

These ruins are all that remain of what a Spanish barrack that likely housed a quarry overseer, masons, and stone cutters involved in the construction of the Castillo de San Marco.

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

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

Dubbed the "smallest church in America," this tiny sanctuary was a local grocer's dream come true.

The language and heritage of a nearly forgotten culture can still be explored in this Southern enclave.

This 19th-century building inadvertently preserved the handprints of its builders within its walls.

A 30-foot man on a penny-farthing bicycle rides along the banks of the Mississippi.

This historic hotel on Bathhouse Row in Hot Springs National Park has a storied history of gangsters and baseball greats.

While knives are the main feature in this store, visitors will also find dinosaur bones and meteorites.

The ghostly remains of an accidental sea.

Hike amid the palm trees that thrive among Southern California's Indio Hills.

A giant desert bird that once swung music fans at Coachella now has a home in a nearby traffic circle.