I'm now in Belogradchik and could hardly believe my eyes when I saw the first rock formations - some 20 kilometres before I hit the town. They extend over a 600-700 sq km area. The area is very poor - I detoured to the old carpet village of Chiprovitsa in an amazing bowl of mountains. A sleepy and disconsolate place - with many Trabans in the area. I had expected to see carpets displayed in the street - but all was desolate with only a small shop displaying very expensive stuff - 5 times what I had paid for an old carpet!
There is a very nice write-up of the Belogradchik rocks and town here.