Bahardena Cave
libre 9
Bahardena cave is located on the northern slope of Kopetdag, 15 km southeast of Bahardena station. It is quite well studied and described by many researchers. The Bakharden cave is excavated in strongly fractured Upper Jurassic limestones containing gypsum interlayers up to 8 m thick.
Its formation, according to M. A. Rotko (1958), is associated with the impact on gypsum and limestone rising sulfurous water in the zone of the Kopetdag line of thermal springs confined to the tectonic fault.
Baharden Cave begins with four entrance openings, the lower of which, the largest, has the form of an arch 6.5 m high. 
In the far part of the grotto, 90 m from the entrance, karst sinkholes are developed. The most significant of them reaches 25 m in diameter and 6.5 m deep.
The second grotto of the cave is almost completely occupied by the famous Kou Lake, which is characterized by crystal clear, slightly mineralized water with a smell of hydrogen sulfide.
The lake is 72 meters long, 30 meters wide, and the greatest depth is 12 meters. Its shores are rocky, the walls rise almost vertically, passing into an uneven stone vault 6-8 m high. The water level in the lake is 61.74 meters below the entrance to the cave. The water temperature is 34-37°.
The lake is flowing, the level changes during the year are insignificant. It has balneological value. The Bakharden cave is warm. The air temperature here varies from 20-25° in winter to 27-32° in summer.
Due to the impact of rising sulphurous waters and hydrogen sulphide released from them on limestone, complex geochemical processes take place in the cave. Along with underground leaching of limestone there is displacement of carbonic acid from carbonates by hydrogen sulfide and interaction of hydrogen sulfide with calcium, which leads to the formation of gypsum, crystals of which cover some parts of the walls and vault of the cave.
These processes are especially active in summer, when due to weak air circulation in the cave hydrogen sulfide vaporization reaches the highest concentration.
Bakharden cave and its fauna
Peculiar and interesting is the animal world of the Bakhardenskaya Cave. Here live bats, rodents, birds and about 50 species of invertebrates. Among the bats there are common long-winged bat, sharp-eared noctuid, large horseshoe, Blasius's horseshoe and southern horseshoe.
Their numbers are enormous. In summer time the number of bats in the cave reaches 150 thousand individuals. The flight of bats from the cave in the evening after sunset is very interesting. At first they fly in one by one, and then, as darkness falls, many thousands of them, forming a continuous live stream.
For the winter the mice fly away. Rodents (Persian gerbil, mouse-like hamster) also live in the Bakharden cave, and some birds nest in the front, illuminated part (Turkestan blue pigeon, Bluethroat, Bluethroat, Cinquefoil, field sparrow).
