A stratovolcano located in the south of Iceland, with a long history of charted activity and a rich mythology attached.

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

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

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

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

In a long-dry lake bed, these groups of massive stone pillars bear a striking resemblance to clumps of everyone's favorite fungi.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.

UNESCO-protected ancient burial ground.

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

"Holy Wisdom" overlooks the city that became its namesake.

A flamboyant five-story building in Bulgaria resembles a crawling snail.

A half-mile long and three stories high, this bridge over the Des Moines River Valley mimics a descent into a mine shaft.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Ancient Egyptian relief, claimed to depict an electrical light.

Light still pours into the ruins of this ancient Islamic observatory.

The world's second-largest sundial, made entirely out of stone.

Native Americans built this circle of stones, which was used to predict astronomical events.

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

Centuries before the modern seismograph, Armenian monks measured quakes with this tilting pillar.

An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.

The angel of death appears to weep black tears at this grave marker.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.