It is the common name of 3 caves lined side by side in Ereğli, 50 km from the city center. These caves were developed within volcanoclastic rocks. Two of the caves have lakes. The first cave consists of 2 parts. There is a mosaic decorated with plant and geometric motifs on the floor of the first section.

The second cave is about 10 m high on the roadside and is named Koca Yusuf Cave by the locals. The third cave is the largest in terms of surface area. Its floor is covered with ground water. The cave, built with human hands, served as a water cistern for the first and second caves. Cehennemağzı Caves has features such as being an important prophecy center of the first age and a place of worship for the first Christianity.