The Trigradska River had deeply cut in the marble rocks the famous Тrigrad Gorge, several kilometres long. Before entering it, the river falls into the Dyavolskoto Gurlo (Devil's Throat) - a fantastic cave, where, along the following 7000 metres, the water forms some 18 waterfalls and passing through the enormous Roaring Hall exits into the canyon. This miracle of nature is electrified.