G-05 Gökgöl Cave, with a total length of 3,350 meters, is the tenth longest cave in Turkey and the second longest in Zonguldak. Inside the cave, which has an 875-meter walking path, there is an underground stream, the flow of which increases in rainy periods. The interior of Gökgöl Cave is extremely rich in terms of drip stone accumulation. The sections of the cave from the entrance to the great depression hall are named as Fossil Entrance, Astım Hall, Hall of Wonders and Hall of Miracles. Stalactites, stalagmites and columns formed by their combination, flag dripstones and dense pasta stalactites on the stream are among the structures worth seeing. Gökgöl cave is one of the important caves for climatic and paleoclimatic studies. The formation of stalactites and stalagmites in the cave, which dates back several million years, continues today. The sediments in which the cave is located include marine limestones, shales and dolomites from the Late Devonian and Early Carboniferous (372-328 million years ago). While the underground waters formed the cave by eroding and melting the limestone layers formed millions of years ago, on the other hand, the stalactites were formed by the redeposition of the calcium carbonates in the composition of the water. As the underground waters passed through the limestone successions that are the remains of the ancient Paleotethys-Reyik ocean, they also revealed the remains of organisms such as coral fossils representing marine life from millions of years ago. Today, these fossils dating back 372-328 million years can be seen on the walls of the cave.

Gökgöl Cave has a microclimate feature due to the fact that the temperature and humidity do not change much during the year. Due to this feature of the cave, it is also used in the treatment of respiratory tract (asthma) patients, and the cave has a great importance in terms of health tourism. Gökgöl Cave, which was opened to tourism in 2001; It has an important tourism potential in terms of industrial and geological heritage elements with its different concept lighting, disabled-friendly walking paths, glass bridges, viewing terraces and the newly completed gift shop, visitor center, toilet and parking lot, as well as being located right next to the Ankara-Zonguldak highway. It is a strong tourism value with the advantages of being close to the city center of Zonguldak