Double spiral staircases are not unheard of, but they are very rare.

Home to the oldest operating roller coaster in the Southern Hemisphere.

An Art Nouveau gem hides beneath the layers of city grime obscuring this once-magnificent building.

A sixth-century Byzantine cistern hidden below a modern carpet store.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

A museum and shop on Bourbon Street located in the former home of the second Voodoo Queen of New Orleans.

Architectureal fantasy quarter of Rome.

An unusual round church in London with a Templar past.

Monasteries on rock pillars, once accessible only by frayed ropes.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

An alchemist's "magic door" stands in the middle of a Roman park.

360° views of the city plus five floors of optical illusions and hands-on science.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

The beautiful baroque library of the Hapsburg empire.

A surreal museum of extraordinary industrial objects.

Hollowed out cedar log tubs set in an ancient towering forest.

A fiery crater has been burning in the Karakum Desert since 1971.

Started as a kitchen garden, now the second largest botanical garden in the world.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

The oldest cemetery in New Orleans, resting peacefully for over 200 years now.

Ruins of a German Castle on top of a towering stone pillar.

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