This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

A giant portrait of an ancient king looms over the river.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

Moss and stone turn this waterfall into an otherworldly liquid veil.

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

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

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

Mysterious standing stone formations looks like a petrified forest.

UNESCO-protected ancient burial ground.

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

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.

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

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

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

An ethereal glowing blue ocean cave in Croatia.

A miniature train-ride through Slovenia's largest cave system.

A whimsical bridge adorned with decorative dragons.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This one-time health resort was used by aristocrats around the world.

This massive subterranean fissure is known as the "underground Grand Canyon."

Man-made mineral caves house massive bat colony.

This disappearing geyser has been attributed to witchcraft, but really it's all about rainfall.

The gutted remains of this Estonian mansion are a monument to a tragic love.