The Trigrad Gorge is located in the farthest southern part of the Central Rhodopes. It is a canyon with a length of over 15 km and 300-meters-tall vertical walls, which at places approach and bend over the road, hiding the sky. The gorge is cut across by the high-watered Trigrad River. Its waters suddenly and majestically disappear into a huge opening leading them to the fearful Diavolsko Garlo (Devil’s Throat). This is a cave with all kinds of utilities. It has an enormous, 36-meter-tall hall, and from its top the Trigrad River waters fall down from a height of 40 m. Crossing the cave, the river disappears again into difficult-to-access galleries, and then flows down through unexplored and impassable siphons. After a distance of several hundred meters, the Trigrad River waters reappear into their bed.