The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

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

A crumbling hospital from the 1850s on Roosevelt Island.

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

A terrific purveyor of natural history objects and curios.

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

Located in the thermoelectric factory that once powered the entire city, this Portuguese museum is shockingly fascinating.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The world's longest outdoor covered escalator system transports commuters through Hong Kong's hilly terrain.

Climb to the top of the world's largest seated bronze Buddha.

A colossal floating restaurant built to look like a ancient Chinese imperial palace.

The Argonaute submarine was the French navy's pride and joy in the 1950's.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

This museum houses an imposing skeleton army comprised of creatures great and small.

The curious underground history of keeping Paris clean.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This massive library holds what was once the largest book collection in the world.