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

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

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

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.

A former bank seized as a sniper vantage point during the Bosnian War is now a secret graffiti art gallery.

The first mosque in the world to receive electricity.

Controversial site of what could be Europe's first pyramid.

This picturesque monastery at the base of a cliff is a peaceful oasis open to all visitors.

The remains of the last Bosnian fortress to fall to the Ottomans are still standing.

This historic timepiece is thought to be the only public clock in the world that keeps lunar time.

Celebrated example of Ottoman architecture that also served as a site for brutal massacres.

An abandoned brutalist monument whose history has been lost to the ages.

This abandoned airplane hanger is said to have once been a top secret launch facility.

The haunting ruins of a military fortress turned astronomical observatory sit on a Sarajevo mountaintop.

This top-secret nuclear bunker hidden in a Bosnian mountain has been converted to a modern art exhibition space.

This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

An early 20th-century sanatorium, long abandoned and now being reclaimed by nature.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

Local lore surrounds this unusual stone.