Ride the subways of yesteryear.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Hidden beneath the streets of London is a secret subway that only carried mail.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

A museum within a museum, devoted to history's most questionable medical devices.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

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

The curious underground history of keeping Paris clean.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A volcanic core jutting above the plain between the Snake and Boise Rivers, a marker identifies the reference point for all U.S. Government Surveys in Idaho.

This giant tower beacon was a key navigation tool for pilots delivering mail amid the night skies.

Supposedly Satanic numbers adorn this preserved submarine sail.

The secluded site of a 1943 plane crash and amazing rescue is only accessible by hiking through the woods.

A museum dedicated to the history and art of staying clean.

This pop-culture shop also offers the chance to become part of their favorite tv show or movie.

It was once used as a classroom to teach mining skills to local high school students.

The mayor made the declaration in 2004.

The world's first nuclear power plant is open to visitors looking to role-play a meltdown.

This museum glorifies the humble potato.

Sweet Willy, at 30 feet tall, is the world's biggest beagle.

Home to the deepest rift anywhere on Earth.

The official atomic museum of the United States explores the explosive and productive history of a much maligned energy source.