Passage 8.54.2
φαίνεται δὲ ὁ Ἀλφειὸς παρὰ τοὺς ἄλλους ποταμοὺς φύσιν τινὰ ἰδίαν παρεχόμενος τοιάνδε· ἀφανίζεσθαί τε γὰρ κατὰ γῆς ἐθέλει πολλάκις καὶ αὖθις ἀναφαίνεσθαι. προελθὼν μέν γε ἐκ Φυλάκης καὶ τῶν καλουμένων Συμβόλων ἐς τὸ πεδίον κατέδυ τὸ Τεγεατικόν· ἀνατείλας δὲ ἐν Ἀσέᾳ καὶ τὸ ῥεῦμα ἀναμίξας τῷ Εὐρώτᾳ τὸ δεύτερον ἤδη κάτεισιν ἐς τὴν γῆν·
The Alpheios, compared to other rivers, clearly displays a special sort of nature in the following respect: it regularly disappears underground, only to appear again. Indeed, having left Phylake and the place called Symbola, it vanishes into the plain of Tegea. Then, resurfacing at Asea and mingling its stream with the Eurotas, it sinks underground for the second time.