Cehennemağzı Caves is the general name for three caves located in the valley formed by the stream once called the Acheron River, which over time came to be known as Ayazma River, Gavur River, and Limanbaşı River. This structure, consisting of three different caves called Church Cave, Chennemağzı Cave, and Ayazma Cave, is also referred to as the Acheron Caves in historical and mythological sources.^【1】 

Used during the Roman and Byzantine periods, the caves were transformed into places of worship and served as an underground church in the early Christian era. The cross figures and religious motifs found in Kilise Cave bear traces of this period. It is believed that during times when Christianity was forbidden, the first Christians in the region used this place as a secret place of worship. In the Ottoman period, the religious and cultural significance of the area diminished; however, the caves preserved their natural structure and have survived to the present day through various narratives.

With great natural and cultural importance, these caves have been seen throughout mythology and history as places of worship, sites for mystical rituals, and a gateway to the underworld. Today, they are preserved as an important area for both tourism and scientific research.

Herakles and Kerberos Legend

Cehennemağzı Caves is associated with the legend of Herakles bringing Kerberos out of the underworld, one of the twelve labors of Herakles. According to this mythology, Herakles’s final and most challenging task was to capture the three-headed dog Kerberos, who guarded the gates of the underworld, and bring it to the surface.

According to the myth, Herakles had to enter the realm of the dead—Hades’s world—to complete his twelfth task. During this journey, the god Hermes and the goddess Athena guided him. After obtaining permission from Hades, Herakles descended into the underworld, where he had to subdue Kerberos using only his strength, as he was not permitted to use weapons. Herakles strangled the beast with his bare hands, subdued it, and brought it to the surface.

In some variations of the legend, the point where Herakles entered the underworld is said to be Cehennemağzı Caves. It is thought that in ancient times, this region was known as the “Gates of Hades” and believed to be a passage to the realm of the dead.^【2】 

Another event said to have taken place at Cehennemağzı Caves concerns the bringing of Kerberos to the earth’s surface. According to the story, when Herakles brought the three-headed guard dog Kerberos out of the underworld into daylight, the beast began to bark fiercely in front of the cave. Foam dripped from its mouth onto the ground, and at that spot, poppies began to grow.

The region where this event is believed to have occurred was named in honor of Herakles’s success. Initially called the city of Herakles, it was later named Herakleia Pontika (Karadeniz Ereğlisi) to prevent confusion with other Herakles cities.^【3】 

Formation and Geology

Cehennemağzı Caves are natural caves formed through karstic processes. Located along the Black Sea coastal belt, they emerged primarily as a result of the erosion of limestone rocks by water and chemical processes over many years. Underground waters and surface runoff gradually expanded the cavities, shaping the caves into their present form.

The geological structure of the region consists of Paleozoic and Mesozoic-aged calcareous rocks. These types of rocks slowly dissolve through reactions with the carbonic acid in water, paving the way for cave systems to form. Stalactites, stalagmites, and travertine formations can be observed on the ceilings and walls of the caves. Additionally, there are erosion marks in some parts of the caves, indicating changes in the underground water level over time.

One of the most striking geological features of the caves is the presence of water pools called “ayazma” (holy water). It is thought that these waters are rainwater filtered through the caves’ karstic structure, becoming rich in minerals over time.

Sections of the Caves

The caves consist of three sections: Church Cave, Ayazma Cave, and the Cehennemağzı Cave. These areas draw attention with their natural limestone formations and the effect of underground waters. Today, they are a significant point of interest for both history enthusiasts and nature lovers.

^{Cave plan (Photo: Turkish Museums)}

Church Cave

Church Cave is a natural formation shaped over time by the carving of rocks. It was used as a church during the Roman and Byzantine periods. Geometric and floral mosaic decorations can be found on the cave floor, where it functioned as a place of worship. However, only a portion of these mosaics has survived to the present day due to damage over time.

On the right side of the cave, there is a niche made for placing a sarcophagus. According to sources, a sarcophagus belonging to Saint Nicholas was once here, but only its place remains today.^【4】  Inside, Roman and Byzantine stone artifacts and niches carved into the walls for placing candles draw attention. Outside the cave, there is a wall built of cut stone and bricks from the Byzantine period, which demonstrates the importance of the cave as a place of worship.

^{Church Cave (Photo: Batı Karadeniz)}

Cehennemağzı (Koca Yusuf) Cave

According to mythological accounts, the legend of Herakles’s labor to bring Kerberos from the underworld is connected with this cave. Its prominence in mythological stories has made it more than just a natural formation—it is a place shaped by legends. Because of its mystical atmosphere and historical significance, it is considered one of the sites mentioned in these legends.

^{Cehennemağzı (Koca Yusuf) Cave (Photo: Batı Karadeniz)}

Ayazma Cave

Ayazma Cave is one of the largest caves in Cehennemağzı Caves and is entirely formed by natural processes. It is believed that its ceiling was leveled with picks and hand axes. On the western side of the cave, there is a large pool, and this pool was among the waters considered sacred during the Roman and Byzantine periods.

In Christian belief, holy water sources are called “ayazma,” which is why the cave is referred to by this name. It is thought that it was used as an area for religious ceremonies in ancient times.^【5】  Given its spacious layout and water source, it is presumed to have been a center where rituals were performed.

^{Ayazma Canve (Photo: Batı Karadeniz)}