The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

This tangled English forest looks like something right out of a fairytale.

This odd Chilean waterfall-cano hotel must be entered via a rope bridge.

An auroral research program that superheats the ionosphere.

A remarkably intact castle that once was the largest in Ireland.

This hidden library of physiological ephemera contains centuries worth of knowledge on the vim and viscera of the human body.

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

Living trees form the structure of an open-air palace.

A favorite haunt of dinosaur loving children and hallucinogen loving hippies alike.

Underground hospital complex constructed by slave laborers during the German occupation of the Channel Islands.

A fairy tale castle in modern Rome.

The show pony of cave systems, Fantastic Caverns manages to live up to its name.

Pompeii's less famous neighbor is still revealing her secrets.

Neo-cave art on the macro scale.

This former insane asylum now holds a pathological anatomy museum.

This Rhode Island mansion was a stand-in for the exteriors of Collinwood in the original "Dark Shadows" series.

Beautiful public park off the beaten path and away from tourists.

At the "Garage Mahal" in Houston, car culture is about more than just driving.

The oldest inn in England served brew to the crusaders.

A cableway for car transport.

An abandoned Indian-inspired mansion.

The true jewel of Africa's west coast known as "Africa's Last Eden."

A curated museum of wooden sculptures inhabits this Russian home.

World's largest collection of serial killer artwork and other macabre exhibits.