America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This innocuous New Mexico storefront was once the secret jump-off spot for Manhattan Project scientists.

Its history includes dinosaur fossils, cattle rustlers, Georgia O'Keeffe, and a mythical giant rattlesnake named Vivaron.

Wedding chapel's mysterious spiral staircase said to be miraculously constructed.

A sprawling collection of over 106,000 toys from around the world.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

"I did this all while you were watching TV."

A multi-storied adobe complex has been inhabited for more than a thousand years.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

This small red school was where Germany signed their surrender during WWII.

An image of the legendary saint stands in the shadow of a cathedral she liberated.

The video game-themed street art first popped up in the French city.

Bits of architecture from a town destroyed in World War I now decorate this hotel garden.

A medieval military street hidden beneath a charming French fishing village.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

This massive blockhead sculpture hides an entire library.

A burial vault located under Tiber Island in the middle of the Italian capital.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

A wunderkammer of curious objects and intriguing art nestled within a hub of ancient Roman sites.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Rome's semi-secret peephole vista is also a former Crusader stronghold.