“If geology is your passion, Bulgaria is great for rock formations and minerals. The Pirin range has some spectacular glacial and karstic features, while the Rodopies abound in odd rock formations such as Miraculous Bridges, The Stone Wedding in the Kardzhali region, awesome caves like Magura and the Devils Throat near Trigrad, and all kinds of gemstones and crystals. In northern Bulgaria the finest formations and rockscapes are at Belogradchik, Vratsa and Iskar Gorges and Sinite Kamani outside Sliven.”
The Rough Guide