This massive subterranean fissure is known as the "underground Grand Canyon."

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

In the past, Renaissance sex workers were encouraged to entice customers on this bridge.

Every inch of this chapel is covered in craftsmanship from across the world.

This triumphal 16th-century arched gateway leads to the oldest street in Palermo.

Why a column on the entrance is inscribed with a verse from the Quran is one of Sicily's many mysteries.

A medieval wash house where people washed clothes in a river allegedly formed by the tears of a mourning nymph.

A lesser-known World Heritage Site with an amazing Byzantine style mosaic of Jesus on the semi-dome of the apse

The world's most active stratovolcano is almost always erupting.

According to Greek mythology, this natural spring is the home of a freshwater nymph.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

This amazingly preserved Doric temple was abandoned before it was ever completed.

Nestled in the hills of Tuscany are gorgeous, multicolored hot springs.

The oldest operating pharmacy in the world features 800-year-old recipes.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

A mechanical clock built in 1914, with a rotation of 12 historical figures on its face.

A set of outdoor stairs named in honor of a famous Austrian artist.

Designed as a reminder of one of the darkest moments in Austrian history.

A gift from Emperor Franz Joseph I to his wife.

In the middle of a Vienna square, Roman ruins dating back some 2,000 years are on display.

Along the edge of this fountain are 365 smaller fountains that represent the days of the year.