An Inca spa, military outpost or maybe… both?

A Christian monastery stands on what was once a holy Incan temple.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

Visiting dignitaries and Hollywood stars once stayed at this 1920s hotel, alongside ghosts that are said to haunt its corridors.

A shrine honoring a legendary ghost bride lies within this vibrant temple.

An ancient capital city that dates back 3,000 years and harbors many surprises.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

A little sculpture with a large wardrobe.

What looks like a normal building is really a hollow facade hiding a subway vent.

A rare water-powered funicular, it uses a huge tank of water and gravity to do its work.

A famed artist's inspiring work of peace and tolerance.

While you wait to cross the street at a traffic light in Mainz, you might notice that the light is staring back at you.

A stunning Victorian abbey and walled garden on a lakefront.

This ancient Irish landscape boasts hundreds of legendary ruins.

Destroyed numerous times, this centuries-old bridge has always been rebuilt with its original design.

Machismo turned on its head: the lady's hand goes to the dude with the bigger brain.

These elaborate gothic monuments honor Verona's medieval lords.

An exotic wildlife habitat right off The Strip.

This fortress-like monastery is covered with intricate frescoes.

Crossing a suspension bridge above a forest is the only way to reach this 12th-century monastery.

Mysterious standing stone formations looks like a petrified forest.

This massive underground salt mine now holds a sci-fi theme park in its depths.