The village of Mostovo is situated on a rock terrace of white marble, terminating in an abrupt cliff. Underneath, the two entrances of Gargina Dupka are situated. The cave name comes from the alpine chough (in Bulgarian – “Haydushki gargi”) nesting near the entrance.
A stream runs out the lower entrance, the upper entrance is overgrown with Hedera helix. After the entrance, the gallery goes up until reaching the first chamber. It is high and lit by the light which comes from the second entrance. In spring and late in autumn, as well as after long rains, in this place a big shallow lake is formed. The way inside is through a 2.5 m waterfall. After a meandering gallery we reach the Bat Chamber, with guano. The second gallery goes right. The floor is muddy, the walls are covered with dendrites and secondary formations. Through two shallow wells, it is possible to reach the underground stream. The way further is hindered by the low ceiling (15 cm). After the wells, the cave becomes lower and ends. After a steep climb on slippery guano in the Bat Chamber, we reach a narrow ascending gallery. After a five-meter vertical, we enter a chamber. A narrow bling gallery follows.
Cave “Gargina Dupka” has been declared a protected area on 04.08.2003 and the main reason for this is the conservation of the habitat of rare and protected bat species. Its inhabitants are the rare and protected species of bats – Greater horseshoe bat (Rhinolophus ferrumequinum), Lesser horseshoe bat (Rhinolophus hipposideros), Greater mouse-eared bat (Myotis myotis), Lesser mouse-eared bat (Myotis blythii), Long-fingered bat (Myotis capaccinii) and Common bent-wing bat (Miniopterus schreibersii). On the floor, covering an area of 300 square meters and a height of 16-18 meters, you can see bat guano, accumulated for thousands of years.