This mesmerizing medieval monastery-cave complex sits thousands of feet above ground overlooking a valley.

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

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

For over 40 years, this quaint little house has teetered on a rock in the middle of a river.

This outcropping was once home to a medieval monastery destroyed during the Ottoman conquest.

An 11th-century Byzantine church with medieval Serbian history and spectacular views.

A Red Cross memorial museum at the site of the Niš concentration camp that operated for four eventful years during World War II.

This memorial park stands on the site of one of the largest mass executions of the Second World War.

Structure built from the skulls of vanquished foes.

Beautifully carved tombstones fill this unmarked graveyard, uniquely situated near the village's famous stone wine cellars.

These natural stone bridges are the largest on the European continent.

A Roman monument to their own civil engineering prowess.

A giant portrait of an ancient king looms over the river.

Stone age urban planning.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

At this archaeological site, visitors can explore the ruins of the capital of the former Roman province of Moesia.

Ruins of an old water tower that look like a horror-film castle.

Once a beautiful palace, this structure is now known as the ''museum of destruction."

It may seem a little out of place in a tiny village, but the inspiring story of its creation made headlines.

Despite being pillaged and destroyed a number over times down the centuries, this historic church still sort of stands.

A self-proclaimed libertarian micro-state on a tiny bit of disputed territory between Serbia and Croatia.