One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

One of Ireland's most infamous prisons for rebels including men, women and children.

A multi-storied adobe complex has been inhabited for more than a thousand years.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

Tubing through a cave lit with glowworms is a magical underground experience.

A sculpture made of 10 Cadillacs as a monument to the “Golden Age” of the American automobile.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

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

This hidden green space is the city's second largest conservatory.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

This ancient market is often referred to as the oldest shopping mall in the world.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

Five candy-colored villages on the Italian Riviera.

The Pope’s secret escape route.

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

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

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

A beautiful geyser under environmental threat.

The most visited, and possibly most controversial, museum in Germany.

The first declared National Monument in the United States.