These monuments were originally natural grottoes, which tradition assigned as habitations to the local nymphs.
The cavern is divided into four grottoes, with two lateral ramifications which reach to the distance of about a mile and a half from the entrance.
The Mithraic temples of Roman times were artificial grottoes (spelaea) wholly or partially underground, in imitation of the original selcuded mountain caverns of Asia.
Subsequently, artificial took the place of natural grottoes.
From the 4th century onwards its grottoes were the dwellings of Christian hermits, amongst whom John of Lycopolis was the most celebrated.