This subterranean oyster house has been the pearl of Grand Central Station since 1913.

Next to the Leaning Tower of Pisa is a cemetery home to ancient sarcophagi and disturbing murals.

Amsterdam's Red Light District leaves little to the imagination.

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

A blend of art, antiquities, and Americana fill this museum, surrounded by whimsical, enchanting gardens.

Nelson Mandela lived here with his family from 1946 until his arrest in 1962.

One of the world's earliest skyscrapers.

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

The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

Not quite the menace it once was, this monster still has some chops.

It was once nicknamed "the most bombed hotel in Europe."

For part of the year, this innovative greenhouse is painted white to keep the plants from getting scorched.

An eerie reminder to the horrors of World War II.

This unassuming farm complex was once the epicenter of an underground liberation group.

Chelsea's soldiers were given strict orders when crossing this historic bridge.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

A 60-room castle constructed by a horse-racing heir.

A free, canine-friendly alternative watering hole near the more famous Barton Springs.

This quirky collection of furniture also happens to be a public art installation.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

According to tradition this is the oldest church in Venice, but its actual age is a mystery.

Home to an endangered salamander, a full moon celebration, and a large spring-fed outdoor swimming pool.

After the musical legend's death, his memorial was mysteriously graffitied in gold.