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

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

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

A hidden stream deep in the mountains creates one of the largest tufa waterfalls in Serbia.

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

Yugoslavia's biggest underground airport lies in ruins.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Once the home of a hermetic monk, this cave now houses a small church.

One of the biggest Buddhist stupas in Europe, hidden from most locals.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

Inside the Šomoška National Nature Reserve exists a unique rock formation rarely seen in the world.

After 11 years of reconstruction work, Slovakia's finest hilltop chapel complex is finally reopen to the public.

A perfectly preserved hill village where the buildings are painted like white lace.

An unusual cave filled with rare alien-looking aragonite formations.

A gorgeous stone viaduct crosses over a bucolic valley.

Climb around the high waterfalls on series of iron ladders and bridges within the wildest gorge in the Slovak Paradise.

Too much gossip or just missing curfew could land you in here for a couple of days.

This region of Slovakia boasts some of the most plentiful opal mines in the world.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

An underground city of salt.

At first glance, this area seems like just another city park, but the lush landscape hides a dark past.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.