This cave is the second largest in the world and extends inside one of the mountains in the city of Trabzon. The cave includes a number of passages that are estimated to be about 8 km long from inside the cave. Visitors can walk 1 km inside it, where there are stalagmites, stalactites, and beautiful and distinctive water ponds that were formed over millions of years. Chall also has a natural aeration system, and it is believed that the stream water that springs from within it contributes to the treatment of sinus infections and asthma. The cave attracts about 25,000 nature-lovers tourists annually, and those in charge of the cave seek to develop its facilities and corridors to accommodate larger numbers of tourists in the future.