This fantastical waterfall is hidden in a cave located in a cracked cliff.

Medicinal spa created with the discharge from a geothermal energy plant.

Rising from the sea like a stone monster.

Staves, storm-calling, and of course, necropants.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

These natural cliffs look like they are a part of an old castle complex.

A vast Communist-era exhibition space in the Bulgarian capital.

An unfinished complex built for children from around the world sits abandoned on the Black Sea coastline.

Mysterious standing stone formations looks like a petrified forest.

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

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

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

UNESCO-protected ancient burial ground.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

A striking symbol of the Bulgarian capital.

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.

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.

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

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.

This abandoned secret city is a crumbling wonderland of Soviet ruins.

This ornate church has survived Nazi and Soviet occupation, including a short stint as a Soviet-era gymnasium and cinema.