Once the tallest building in the world and the site of "the highest dinner ever held in New York" this building now holds the most expensive penthouse in the city.

This empty Victorian manse on Staten Island is said to be haunted but is actually a real life crime scene.

An abandoned castle owned and ignored by Masons carries a cursed history.

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

Ride the subways of yesteryear.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

Enormous sandstone towers loom within a Czech forest.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

Lavish royal estate punctuated with heated greenhouses.

This 135-year-old weather station studied the effects of the climate on human health.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Sweden's "good old days" painstakingly re-created in a model village.

Stockholm's deepest subway station is also a stunning ecological wonder.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

One thousand trees were planted in Norway to be used to print books a century from now.

Explore nearly 400 years of English middle-class home life.

Eclectic final resting place of the controversial explorer.

This home on a quiet suburban street is completely covered with vibrant mosaics.

The pioneer of psychoanalysis spent the final year of his life here, still seeing patients on that famous couch.