Cerje Cave or Cerjanka () is a cave in southeast Serbia. With the length of , it is the second longest cave in Serbia after the long Lazar's Cave.
Location
The cave is located east of the village of Cerje in the Municipality of Pantelej and north of the City of Niš.
Geology
Entry into the Cerje cave is situated on the western side of the Kalafat mountain, in the wider area of the Kamenički vis plateau. Entrance is located at the point where the river of Provalijska reka sinks underground. The cave itself is hydrologically active. Geologists estimate that the cave is some 2 million years old.
The cave is characterized by the small and narrow entry section and the large dimensions of the Main corridor, which is mostly over , but also up to high, which points to the different genesis of the two features. Right behind the ending of the low entry section, a large fossil canal was discovered. Today it ends with the plug of blocks, but it is believed that it represents the connection with the old entries into the cave which are now buried under the eroded sides of the amphitheater which marks the ending of the Provalijska reka's blind valley. The Cerje cave is a wet cave. Even during the summer, when the river dries out, there are ponds at the entrance. Further in the cave, the water flows for through the Main corridor, up to the siphon. Other corridors, including the High canal (which is above the central flow), even though they have water in the eroded holes, doesn't seem to have an active water flow. Area of the cave between the siphon and the "Salomna chamber" is called the Moon canal and is carved in the black limestone, eroded into sharp, pointy forms. Eroded water holes are everywhere and the upper sections of almost all corridors, even those deep in the cave, are abundant in allogenic pebblestone and gravel which remained in the niches. It shows that the entire cave was once filled with the allogenic material which was later washed away. Geology had to be different at that time as the modern topography and hydrography in the surrounding area of the cave does not point to the river flow so powerful to wash away the cave. Ceiling of the cave is partially made of an unusual mass which has an appearance of the decomposing limestone. Microscopic analysis showed that the limestone used to be altered by the thermal waters. Today, there are several thermal springs at the foothills, west of the cave, but the role of these thermal springs in the formation of the cave has still to be explored.
The cave was explored for the first time in 1976 by the members of the Belgrade Mountaineering Union when it was established that the cave was long which, at the time, made it the longest cave in Serbia. Plans were made to turn it into a touristic attraction so the narrow entrance was widened by the explosives and the silt brought by the Provalijska reka was removed. However, the job of turning it into the touristic destination was never achieved. Since the 1970s, the river has washed away the beams which were placed in 1976 to function as the bridges and again brought silt which turned the entrance into the narrow passage, up to high, that can only be passed by crawling. Thought to be completely explored, the cave was left unattended until the fall of 1995 when the members of the Student speleologic and alpinistic club (ASAK) explored the cave again and discovered that there is an extension to the main corridor. In July 1996 they returned and discovered of new corridors, raising the overall length to , with the total depth of .
The Provalijska reka, which enters the cave at an altitude of , springs again as the well of Kravljansko vrelo at an altitude of , northwest of the entrance into the Cerje cave. Explorations in 1996 established that the Kravljansko vrelo is away and beneath the siphons which mark the end of the cave. Dye tracing conducted in the 1970s proved the connection between the cave and the well of Kravljansko vrelo, but members of ASAK wanted to dive through the well to the cave. Due to the technical problems, they had to quit at the depth of .