Subsequently, artificial took the place of natural grottoes.
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.
The Mithraic temples of Roman times were artificial grottoes (spelaea) wholly or partially underground, in imitation of the original selcuded mountain caverns of Asia.
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.