Katal-e khor is an amazing cave which mostly contains lime stalactites, stalagmites, huge halls and mainly dry corridors. Located about 400 km west of Tehran, it is considered as the most famous natural phenomena in Zanjan Province.
The cave was scientifically studied at 1984 and due to the results, formation of the cave referred to the Jurassic period (about 120 million years ago).
The ancient cave dwellers lived at entry stages and the bones of about 80 persons are still preserved.
Currently, the cave has been divided into cultural, recreational, and sports divisions. The sports division is simply used by cliffhangers and spelunkers although its total area has not been explored.
The cultural division is located at the southern part of the cave generally a natural corridor which is used for various ceremonies.
Narrow galleries in different directions can be found inside vestibules whose area sometimes reaches over 200-300 square meters. Some of them are deadlocks and others have narrow passages to other vestibules. Many of those paths and passages have not been explored yet.
Hence, there are two visiting routes inside the cave, a two-kilometer-long straight route for public visit and a four-kilometer-long sport route for professionals.
The most beautiful natural phenomenon of the cave comprises spectacular stalagmites which can be seen around springs and lagoons at its bottom. Due to penetration of water into lower layers of the cave and shallow lagoons, crystalline stalagmites have created very beautiful vistas.
In terms of the quality of crystals, stalagmites, beauty, and the number of its levels, Kotal-e Khor cave is a well-known natural phenomenon in the world. In terms of antiquity, the cave is as old as Ali Sadr Cave in Hamedan. Of course, the two caves are different from two viewpoints. Firstly, Ali Sadr is full of water, but Kotal-e Khor is almost dry.
Secondly, limestone at Kotal-e Khor is purer compared to Ali Sadr and this has made the cave more beautiful because the more pure limestone is, the more transparent it is and the light would pass through quite easily.
A remarkable point about the cave is that studies have shown that the cave finally leads to Ali Sadr Cave. Another wonder of the cave is the number of its levels, which are very rare among major caves of the world.
According to estimates, the first 700 m of the cave has a diameter of about 70 cm so that early spelunkers had to crawl on their chests and blaze the trail. The 100 m that follows has been an abode for prehistoric man and this has been confirmed by discovery of 80 human skeletons.
A unique feature of the cave is its huge lime columns which are the product of fusion of limestone stalactites and stalagmites. The columns act as natural props which prevent the cave’s ceiling from collapsing.
During 120 million years of its life, the cave has changed many times with earthquakes, faults, and collapses being among the most common natural changes which have taken place inside the cave.