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

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

Yugoslavia's biggest underground airport lies in ruins.

A war-torn Olympic relic is being overtaken by graffiti and nature.

Longest fortress system anywhere in Europe.

An autonomous republic of Orthodox monks.

A spectacular cave and a beguiling lake.

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

A naturally beautiful, seemingly bottomless deep blue spring.

What happens when you cross a mayor and a painter?

An Albanian monument to the Communism that nearly crushed the country is now a crumbling wreck.

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

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

Moss and stone turn this waterfall into an otherworldly liquid veil.

The Natural History Museum that time forgot.

The largest catacomb system in the world.

A stunning 18th century pharmacy and medieval chemist's collection.

Packed to the ceiling with antique taxidermy and hunting arms.

A unique collection of Soviet military artifacts lies hidden away in a disused train, in the unrecognized Eastern European republic of Transnistria.

The largest wine cellar in the world is a 150-mile network of underground caves near the capital of Moldova.

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

Popular river that runs through the remote Serbian municipality of Leskovac.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

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