G-14 Cumayanı and Kızılelma caves are a single cave system connected to each other by a series of sinkholes. The waters sinking from the Kızılelma Cave, sink again with a siphon right after leaving the Cumayanı cave. With the ongoing flow, the waters come out of the Cumayanı district and reach the sea with the Cumayanı stream. The Cumayanı cave, which has a length of approximately 1 kilometer, was developed within the Lower Cretaceous aged Kapuz formation. The Cumayanı cave system is of great importance in understanding the karstic drainage and the underground reservoir-aquifer relationship.

Cumayanı cave is also the richest cave in Zonguldak in terms of bat species as well as its geological features. During the researches, it was determined that 9 bat species (Rhinolophus ferrumequinum, R. euryale, R. hippodideros, R. blasii, Miniopterus schreibersii, Myotis capaccinii, M. myotis) live in this cave.