There is no evidence of the existence of a cult of Caelus, the occurrence of the name in dedicatory inscriptions being due to Oriental influences, the worship of the sky being closely connected with that of Mithras.
In 1617 Napier published his Rabdologia, 4 a duodecimo of one hundred and fifty-four pages; there is prefixed to it as preface a dedicatory epistle to the high chancellor of Scotland.
Remains of a Roman thermal establishment exist near the principal spring, the so-called Lago della Regina (which is continually diminishing in size owing to the deposit left by the water), and dedicatory inscriptions in honour of the waters have been found.
There can be no doubt about the identity of the building, for the basis on which it stands bears the remains of the dedicatory inscription, stating that it was erected from the spoils of Marathon.
A dedicatory inscription runs along the face of the top step, and has been the subject of much dispute.