A high mountain range runs along the African coast and separates the Nile Valley from the Red Sea; Berenice was sited upon a narrow rim of shore between the mountains and the Red Sea, at the head of the "Sinus Immundus", a south-facing bay sheltered on the north by a high peninsula then called "Lepte Extrema", and to the south by a chain of small islands scattered across the mouth of the bay. One of them was called the Island of Ophiodes () and was one of a few sources of gemstones local to Berenice. The harbour is marginal, but was improved by engineering.