Most-visited and most-photographed slot canyon in the American Southwest.

One of the longest water bridges in the world was built over a supposedly haunted swamp in Louisiana.

The world-record holder for the longest bridge stretching continuously over water.

This now-deactivated naval base defended the Florida coast for centuries.

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

A tunnel with windows, so you don't miss out on the impressive views.

The oldest U.S. Government building in California, and it's State Historic Landmark #1.

Fake rail crossings mark the site of an influential doctor's demise.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Intertwined, interspecies trees which locals believe can grant boons to lovers.

St. Augustine's record-setting narrow street was designed to protect against pirates.

It's a pretty creepy lock-up.

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

Must form and function forever remain at odds? Not if the Florida Department of Transportation has its way.

This distinctive Crescent City tradition dates back to the days of horse-drawn carriages.

This Art Deco airport was once deemed “the air hub of the Americas.”

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

This Mississippi seminary was the first in America to train Black Catholic priests.

A local landmark with generations of spraypainted messages, and more being added each day.

Pensacola's UFO home has withstood many hurricanes—just as the experimental 1960s design intended.

Scenic mount trashmore, Virginia Beach's most curious waterfront still has a couple of secrets.

The land is home to swimming ponies and a legendary 18th-century treasure.

This 16-foot, intricately detailed model of the Gearing-class destroyer has been called the most detailed model ship ever built.

Rediscovered after a century, the father of the American Navy was reinterred in something dredged up from Davy Jones' Locker.