Passage 8.44.4
τοῦ δὲ Εὐρώτα τὸ ὕδωρ ἀνακεράννυταί τε πρὸς τὸν Ἀλφειὸν καὶ ὅσον ἐπὶ εἴκοσι σταδίους κοινῷ προΐασι τῷ ῥεύματι· κατελθόντες δὲ ἐς χάσμα ὁ μὲν αὐτῶν ἄνεισιν αὖθις ἐν τῇ γῇ τῇ Λακεδαιμονίων ὁ Εὐρώτας, ὁ δὲ Ἀλφειὸς ἐν Πηγαῖς τῆς Μεγαλοπολίτιδος. ἔστι δὲ ἄνοδος ἐξ Ἀσέας ἐς τὸ ὄρος τὸ Βόρειον καλούμενον, καὶ ἐπὶ τῇ ἄκρᾳ τοῦ ὄρους σημεῖά ἐστιν ἱεροῦ· ποιῆσαι δὲ τὸ ἱερὸν Ἀθηνᾷ τε Σωτείρᾳ καὶ Ποσειδῶνι Ὀδυσσέα ἐλέγετο ἀνακομισθέντα ἐξ Ἰλίου.
The water of the Eurotas mingles with that of the Alpheios, and for about twenty stadia they flow onwards in a single, common stream; but afterward, descending underground into a chasm, one of them, the Eurotas, comes up again within the land of the Lacedaemonians, while the other, the Alpheios, emerges at Pegae in the territory of Megalopolis. From Asea there is an ascent to the mountain called Boreion, and at its summit there are visible remains of a sanctuary; it is said that Odysseus, after returning home from Troy, founded the sanctuary there for Athena Soteira and Poseidon.