An artist's cute bronze subway sculptures belie his violent artistic past.

During the holidays, a vintage subway train whisks New Yorkers back in time.

A trove of century-old litho stones from the Puck Building's printing days were discovered behind a cellar wall, and are now hanging in the store.

Plot your trip through the city on the sidewalk.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The walls of the iconic dome are hollow and have a secret stairway.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

Inside a former cabaret, seven floors of erotic art.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

France's national museum of scientific and industrial instruments.

This museum houses an imposing skeleton army comprised of creatures great and small.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

A haunting collection of the vanished and disappearing natural world.

This ancient tunnel is one of the most important examples of Roman hydraulic engineering in Spain.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

Numerous sculptures set along hiking trails symbolize and idealize the relationship between man and nature.

Strange masks and obscure costumes are housed in this old Madrid corrala.

This small chapel is built of human bones and decorated with a golden skeleton.

The remains of an entire Roman city can be explored in this interactive museum.

A relic of World War I that now exist as a piece of public art.