Cliffside houses provide a spectacular view from their perch above the valley.

The site of the first medieval crusade that pitted Christians against Christians.

These ruins are all that remain of Tortosa’s lost coal gas manufacturing industry.

The world's largest solar furnace uses 10,000 mirrors to concentrate the sun's rays to generate power.

This extraordinary, multi-pillared monument depicts the fascinating history of Georgia.

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

Ancient rock-hewn town that witnessed key events of Georgian history.

A gleaming white and undulating tower marks the border between Georgia and Turkey.

The ruined doorway is a portal to the building's turbulent and torturous past.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This tiny island is home to the world's largest colony of Northern gannets.

Europe's highest peak is a key pillar of the Seven Summits mountaineering challenge.

Monks in the empyreal Alazani River valley have preserved their 1,000-year-old winemaking tradition.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

The oldest surviving synagogue in New York City is now a soaring art space.

Home of the first female Hungarian poet, where her secret writing lay hidden for over a century.

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

Legend says these stone structures are where the doomed citizens of a vanished village sent themselves to die.

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

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

Its front wall is striped with a menagerie of fantastic beasts and magnificent monsters.

A long spiraling walkway winds through the woods, and around a copper beech tree at the center.

Thanks to its heroic service during WWII this Soviet castle has been turned into a monument towered over by a brutalist titan.