Passage 7.27.8
ἔστι δὲ καὶ Εἰλειθυίας Πελληνεῦσιν ἱερόν· τοῦτο ἐν μοίρᾳ τῆς πόλεως τῇ ἐλάσσονί ἐστιν ἱδρυμένον. τὸ δὲ ὀνομαζόμενον Ποσείδιον τὰ μὲν ἀρχαιότερα ἦν δῆμος, ἔρημον δὲ ἐφʼ ἡμῶν. ἔστι μὲν δὴ τὸ Ποσείδιον τοῦτο ὑπὸ τὸ γυμνάσιον, διαμεμένηκε δὲ καὶ ἐς τόδε ἔτι αὐτῷ Ποσειδῶνος ἱερὸν νομίζεσθαι.
The Pelleneans also have a sanctuary of Eileithyia; this is located in the lesser part of the city. The place called Poseidion was formerly in ancient times a populous settlement, but is deserted in our day. This Poseidion lies below the gymnasium, and even in my time a sanctuary of Poseidon continues to be held in honor there.