Outstanding, eerie frescoes and decorations fill this 19th-century monastery.

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

Rock carving created 1,300 years ago 75 feet off the ground.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

Mysterious standing stone formations looks like a petrified forest.

The remarkably well-preserved final resting place of a powerful ancient Thracian king.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

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

Sofia's legislative center is continuously reinventing itself.

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

A striking symbol of the Bulgarian capital.

UNESCO-protected ancient burial ground.

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

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

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

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

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

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

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.

It was once nicknamed "the most bombed hotel in Europe."

Belfast's namesake river still winds below the city center, hidden from sight.