Ancient rock-hewn town that witnessed key events of Georgian history.

Underground monastery and fortress.

Not far from a popular beach, an unfinished, abandoned mansion for Bulgaria's last communist dictator.

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

The social hall of this former factory is a Communist-era time capsule.

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

A mysterious tunnel hidden in the shadows of a colorful, historic sanctuary.

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

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

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.

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.

Abandoned medieval hill town.

The fairy tale castle of the "fairy-tale king."

The great Danube river starts here.

This ancient ruined monastery has been destroyed by fire so many times that it seems like God hates it.

A Black Forest cuckoo clock theme park features one timepiece big enough to walk inside.

Trek up this glacier before it disappears.

An icy lake tucked among jaw-dropping alpine panoramas.

A suspended footbridge allows for traversing this gorge carved through the French Alps.

Since ancient times these picturesque springs have been providing bathers with healing waters.

The top of society once luxuriated in this world-class hotel, which continues to impress, even in ruin.