This little museum is built on a theater that was once a wildly elaborate speakeasy.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

A beautiful 62-acre Catholic shrine and botanical garden.

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

A heavenly experience, right here on Terra Firma.

Once the most densely populated place in the world, this island is now a ghost town.

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

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

A museum of carnival attractions where you are invited to ride the rides.

Paris' linguistic guide to the international language of, yes, love.

Home to items never before seen by the public.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.

James Turrell's total color immersion art installation, hidden on the top floor of a luxury handbag shop.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

The first declared National Monument in the United States.

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.

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

A strange house built only at night, with rumored mystic inspiration.

This shop for all your super spy needs hides an educational secret.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.