Ride the subways of yesteryear.

This innocent-looking townhome is actually a subway exit.

In the middle of downtown Brooklyn lies a 165 year old secret hidden right below the surface (closed to the public indefinitely).

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

More than 250 sakes are available in an izakaya hidden in the basement of a Midtown office building.

An unfinished rail tunnel that has since been used to house cheese and bats.

Italian cave with exceptional acoustics and an unsavory history.

A watering hole where the options for seating include a bar, patio, or subterranean cave.

Some islands... they come, they go, especially on Lake Travis.

This underwater old Texas hill town only resurfaces during harsh drought.

This beautiful grotto is one of those places where you can't believe you're just outside Austin.

Civil War dumping ground for the bodies of terrorized Union sympathizers.

An Aztec snake god has taken the material form of an apartment complex.

A boat ride through utter darkness, lit only by headlamps, reveals an emerald green pool locals believe is sacred.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

Largest cave system in Africa.

Abandoned for 60 years, this submerged bridge was completely forgotten until the lake was drained.

The scant remains of this flooded historic village can be explored in one of the most remote areas of the Great Smokies.

An abandoned town is hidden in Great Smoky Mountains National Park.

Mile-long cave system near Great Smoky Mountains.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

What looks like a link in Gondor's early warning system is actually a centuries-old Italian fortress.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.