In the Ozarks, a waterfall shoots out from a glorious hole.

Steepest flood safety railway in the entire world.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

The headquarters of the Fraternitas Rosae Crucis, complete with Rosicrucian pyramids, all in the Pennsylvania woods.

A mine fire has been burning under the deserted town since 1962, but this church is still going strong.

The graffitied ruins stand hidden within the Pennsylvania woods.

Over 100 concrete munitions bunkers are all that remain of a Pennsylvanian village seized by the US government.

In which a local geological marvel becomes a quaint roadside attraction.

An abandoned stretch of highway, deteriorating next to the operational one.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

A toxic ghost town sitting atop a massive coal fire.

More than 7,000 gallons of water pour over these cascading red quartzite waterfalls every second.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

A once grand hotel is being retaken by the wilderness it once capitalized on.

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

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

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

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.