Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

Beautiful carved tunnels.

This 1,400-year-old abbey was once a powerhouse for music and intellectualism known across Normandy.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

Abandoned since 1998, this train station has become an oasis for urban explorers.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

Hidden up a dusty track off the Georgian Military Road is this fascinating waterfall with mountainous views.

Take respite inside this jaw-dropping church while climbing the volcano where Georgia's Prometheus was once chained.

Georgia's answer to Easter Island immortalizes the nation's great poets, artists, and leaders in stone glory.

A cylinder monument with a spectacular vista commemorates a friendship that some say never existed.

Fortified homes of highland warriors that are still in use today.

Despite being tiny and rural this Georgian airport looks like a sci-fi boondoggle.

The second-deepest known cave on Earth, hidden in an extremely remote mountain region.

Veryovkina Cave is more than 1.3 miles deep—the deepest known in the world.

The second largest in the world, this massive underground void has its own subway.

Ruins of a former government building destroyed during the Georgian-Abkhaz war in the wake of the fall of the Soviet Union.

These Stalin-era industrial 'death traps' hang lifeless above the city

Small church on top of a huge rock column.

This neon lit Georgian cave claims to hold the boulder Prometheus was chained to.

The decaying remains of a once-luxurious Soviet spa town.

The cave holds a spectacular array of stalactites and stalagmites, including one shaped like a giant human heart.

A shipwreck named Desire at the shore of Batumi.