Inside houses a vast collection of military aircraft and missiles spanning the ages.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

The Pennsylvania landscape depicted by a quarter mile of mosaics made from used road signs.

The last street in Pittsburgh that's paved with wood.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Welcome to old Florida, where a 1940s mermaid show is still enchanting visitors.

Step into the past and experience what life was once like in the Sunshine State.

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

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

A natural gas leak provides a flickering flame beneath a waterfall.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

This Wall Street bar was once a hub of revolutionary activity where Washington famously bid farewell to his troops.

One of only two commuter aerial tramways in the United States.

A crumbling hospital from the 1850s on Roosevelt Island.

This elaborate towering structure was once famed for its revolutionary height.

Yo, Adrian!

World's first "penitentiary," meant to be humane, drove men insane.

Washed out by the Johnstown Flood in 1889, the surviving portion of the original two-span bridge now resides at Fishing Creek.

I-95's Tijuana-style celebration of kitsch at the Carolina border.