G-15 It is a cave in the city of Zonguldak province and is located on the seaside, 15 kilometers from Kilimli road. The cave, which has a total length of 800 meters, is entered through the fossil mouth facing the sea. After a hole in which a person can only fit in from 50 meters, it continues with an underground stream in places. There is a siphon at 400 meters and it can be passed on foot when the waters recede. From here, it proceeds another 400 meters and ends with a siphon.