The Devil’s Throat is an abyssal cave that is formed as a result of a collapse of the Earth’s layers. The cave descends straight down without branching in either direction. The water from the Trigrad River falls from a height of 42 meters down the cave’ “throat”, making it the highest underground waterfall on the Balkan Peninsula. Because of the muffled roar of the waterfall, the cavern into which it falls is known as The Hall of Thunder. It is enormous – the second largest cavern in Bulgaria. Roughly 400 meters from the entrance the water disappears down a funnel. This funnel is more than 150 meters deep, and when it emerges from the funnel into another cavern about 60 meters long, the underground river exits the cave and flows out among the mountain peaks through another cave.
It is an arresting fact that nothing carried into The Devil’s Mouth Cave by the river emerges from it. Many attempts have been made to track pieces of wood and other material through the cave, but they all vanish without a trace on the underground river, arousing curiosity and tantalizing the imagination. Experiments performed with water dyes have shown that it takes more than 1½ hours for the water to traverse the short distance from one opening to the next, fueling speculations about an extensive system of underground streams in the cave.
There are 4 bat species that live in the cave during the different seasons: Rhinolophus ferrumequinum, Rhinolophus hipposideros, Myotis cappaccinii and Miniopterus schreibersii. During the winter, the biggest bat colony of Miniopterus schreibersii in Bulgaria and in the Balkans overall nests here.
In this cave, a colony of over 35,000 species of the bent-winged bat and the long-fingered bat, included in the World Red List, winters. The other two species inhabiting the Devil’s Throat – horseshoe bats – are among Europe’s top conservation priorities. Thus the Devil’s Throat falls into the number of the most important bat shelters in Bulgaria.