A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

This historic black and white monastery is one of Bulgaria's architectural jewels.

The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

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

An abandoned saucer-shaped monument in the Bulgarian mountains.

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

This former Cyprus flight hub is now a crumbling, abandoned ghost complex.

The water here is so clear you can see the mysteriously sunken ship from the surface.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

A magical museum of fairy tale treasures near Cyprus' buffer zone.

150 or so scrounged-up lamps, chandeliers, and lanterns light up this alley in central Athens.

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

An ancient octagonal weather station named for the eight Greek gods of wind.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

This hidden gem is bathed in beautiful natural light.

Unfinished monument to peace between Turkey and Armenia, long divided by a dispute over genocide.

The best-preserved ancient theater in the world.

The ornate miniature mansions were built for Istanbul's feathered residents.

This famous city eluded concrete detection until the early 2000's.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

Acres of English cottage gardens, unexpectedly nestled in a Cleveland suburb.

A slab of sandstone covered with mysterious 1,000-year-old rock carvings from a vanished North American culture.