It’s an old town situated under the Belogradchic Rocks. They rocks are the same kind of sandstone like in the American West. The rocks were used as a Roman Fortress beginning in the First Century AD. Here’s the town:
You can see the rocks above the town. Of course most of the walls you see there were rebuilt over the centuries. There still remains portions of the ancient Roman wall.
It’s quite a climb to get to the top, but the view is worth it.