A forgotten "city of water" underneath the famous Trevi district.

St. Francesca Romana, patron saint of drivers, resides in the church she founded.

The interior of this Serbian royal family's mausoleum is covered with exquisite mosaics.

Through the colossal entrance to this cave you'll find limestone tubs and an underground waterfall.

This natural monument has an origin story steeped in legend.

A sinuous path among steep cliffs creates a stunning sight in southwestern Serbia.

The ruins of this medieval castle on a foggy hill tell the story of a once-mighty empire.

According to a local legend, this old castle could only be built after a woman was immured in the walls.

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

This 16th-century monastery has been turned into a surrealist architecture compound.

The ruins of this medieval castle overlook the lake of Piediluco in what was once a sacred forest.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

A lavish 16th-century mansion filled with spectacular staircases, fantastic frescoes, and gorgeous gardens.

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

This ancient altar emerges from the thick forests to reveal the mysteries of Etruscan sacrificial rituals.

Romans built the world's tallest artificial waterfall in 271 BC.

This long-abandoned village sits across a narrow gorge from a still-inhabited settlement that was once its twin.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

An incredible menagerie of more than 3 million taxidermied animals at the oldest science museum in Europe.

Drink wine handed out through a window as part of an age-old tradition.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

Giant pinnacles in the sun-scorched lands of Southern Utah have been nicknamed "white ghosts."

A Nevada mining boomtown that ran out of silver and luck.

This museum glorifies the humble potato.