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

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

Imperial palace of Emperor Galerius, the Emperor behind the worst Christian persecutions during the Roman Empire.

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

A hidden stream deep in the mountains creates one of the largest tufa waterfalls in Serbia.

A striking symbol of the Bulgarian capital.