ereğli was founded during the 6th century b.c. by the mariandynians, who were the successors of the phrygians. ereğli was an important commercial wharf (emperion), which takes its name from the famous mythic hero, hercules (heracles). the city preserved its importance during the roman, byzantine, seljuk, and ottoman empire periods. important historical ruins in the region include the acheron valley ruins, in which the cehennem ağzı caverns are located, along with hellenic, roman, byzantine and ottoman ruins, ereğli castle, heracles palace, çeştepe lighthouse tower, byzantine water cisterns, krispos mausoleum, byzantine church and halil paşa mansion.