The Mithraic temples of Roman times were artificial grottoes (spelaea) wholly or partially underground, in imitation of the original selcuded mountain caverns of Asia.
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.
On the north-west rock the caves known as the grottoes of Pan and Apollo were cleared out; these consist of a slight high-arched indentation immediately to the east of the Clepsydra and a double and somewhat deeper cavern a little farther to the east.
These monuments were originally natural grottoes, which tradition assigned as habitations to the local nymphs.
From the 4th century onwards its grottoes were the dwellings of Christian hermits, amongst whom John of Lycopolis was the most celebrated.