Flames have been burning within this mountain for more than 2,500 years.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

This Turkish cave boasts some rather bizarre associations with the King of Mount Olympus.

A charming beach town in Turkey captures all the colors of the rainbow.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Roman ruins top white travertine terraces formed by ancient hot springs.

This 3,800-year-old site contains markers used to study the movement of the sun and moon and create a lunar calendar.

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.

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

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

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

Crossing a suspension bridge above a forest is the only way to reach this 12th-century monastery.

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

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.

This historic black and white monastery is one of Bulgaria's architectural jewels.

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 abandoned saucer-shaped monument in the Bulgarian mountains.

Legends of treasure and spirits flow from this this fairy tale-like oasis.

The ridged layers that make up this river canyon represent Earth's geological history.

This fresco inside a Serbian cave church has been a source of disagreement.

An 11th-century Byzantine church with medieval Serbian history and spectacular views.