Read between the lines of the subway map to find the hidden abandoned Civil War fort.

The beauty of urban decay, hiding some dark secrets.

The ancient tomb acts as a calendar that keeps perfect time.

A century-old network of freight tunnels underneath the city's historic business district.

A popular swimming hole that hides one of America's most deadly diving spots.

Tiny effigies of the victims of Edinburgh's famous Anatomy Murders.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

The oldest Italian café in Boston, this spot also serves as a veritable museum of vintage coffee ephemera.

According to the local folklore, the myriad colors of this lake are the result of a lovelorn wizard's blunder.

Ancient cliffs resembling a kilt on Scotland's second largest island emit an entrancing sound.

A castle built by an eccentric medieval enthusiast in rural Ohio.

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

The longest navigable underground river in the United States is home to countless blind and albino animals.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

Thousands of well-dressed mummies below a monastery.

An ethereal glowing blue ocean cave in Croatia.

An abandoned railroad tunnel is now filled with bioluminescent bugs.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

An ancient Scottish rock formation said to be the gravesite of a giant remains ensconced in legend and intrigue.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

A hidden bar inside an ad agency has a deliberately misleading name, so employees can stay late under pretext of paperwork.

19th century pendulum and a clock restored by a rogue group of guerilla artists.