Once an opulent Art Nouveau hotspot, the Constanța Casino is one of Romania's most beautiful abandoned buildings.

A forgotten remnant of the Soviet Union, Transnistria is an unrecognized country hidden behind a heavily militarized border between Moldova and Ukraine.

This massive concrete sculpture is said to be the heaviest communist monument on Earth.

The remains of a sunken military ship wreck visible through clear water.

A muddy alien landscape that is home to rare species of exotic plants.

Oriental bazaar in the heart of Sarajevo.

Bridge that died in war and was resurected.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

This top-secret nuclear bunker hidden in a Bosnian mountain has been converted to a modern art exhibition space.

A naturally beautiful, seemingly bottomless deep blue spring.

Monasteries on rock pillars, once accessible only by frayed ropes.

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

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

This huge metal monument is slowly being stripped to its concrete skeleton.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

These warring psychedelic crags commemorate an unsuccessful military operation.

An ancient Thracian city where fire rituals were practiced on the largest cult altar in Southeast Europe.

UNESCO-protected ancient burial ground.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

An abandoned saucer-shaped monument in the Bulgarian mountains.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

Stone pillars and a petrified wedding party in the hills of North Macedonia.

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

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