The ridged layers that make up this river canyon represent Earth's geological history.

A well preserved medieval fortress in Vojvodina.

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

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

This fresco-covered medieval monastery hangs from the side of a steep cliff.

Religious perseverance and cultural coexistence manifest in an architectural gem that multiple wars couldn't topple.

A maze of underground tunnels beneath one of the most beautiful forts in Serbia.

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.

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

The bizarre rocks of Đavolja Varoš are the result of natural erosion.

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

This spaceship-like Serbian monument reaches for the stars in celebration of the fallen fighters of fascism.

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

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

Structure built from the skulls of vanquished foes.

Legends of treasure and spirits flow from this this fairy tale-like oasis.

A glacial valley filled with silver beech trees in the mountains of Portugal.

This tunnel was built in order to protect the village of Daroca from flash floods during rainy seasons.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.