The oldest stone house in Paris was built by its most famous alchemist.

The ruins of a 15th-century castle that has seen its fair share of bitter feuds.

The way that light hits a stained glass window on a specific day is one of many "clues" to a mysterious treasure.

Centuries after this 12th-century abbey had fallen to ruin, it became known for the strawberries and cream served in its gardens.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

Mysterious installations bring levity and light to a sometimes stodgy city.

This anonymous businessman sculpted in bronze became an enduring memorial after 9/11, and had been mistaken by rescue workers for a survivor in the rubble.

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

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

A celebration of capitalism in Midtown.

World's largest cave was only discovered in 1991, and now offers tours to the public.

One of the world's oldest and most massive living organisms is a grove of quaking aspens.

A local scoured more than 1,000 acres for stone to create his masterpiece.

Does this 10-foot-tall statue carved into a rock face depict a king afflicted by a skin condition or a Buddhist figure?

A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

The remains of "the Pearl of Scotland" can be found inside this church.

This secret Swiss fortress is disguised as a harmless pink house, complete with fake windows.

The remote outlaw hideout of Jesse James, Butch Cassidy, and the Sundance Kid.

A mixture of strange symbols, ciphers, words and cryptograms carved in 1876 remain unsolved to this day.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

Buildings from the fictional planet of Tatooine still litter the Tunisian desert.