Strabo, Geography 17.6
The great lighthouse of Alexandria, on the island called Pharos.
ἔστι δὲ καὶ αὐτὸ τὸ τῆς νησῖδος ἄκρον πέτρα περίκλυστος, ἔχουσα πύργον θαυμαστῶς κατεσκευασμένον λευκοῦ λίθου πολυώροφον, ὁμώνυμον τῇ νήσῳ· τοῦτον δ’ ἀνέθηκε Σώστρατος Κνίδιος, φίλος τῶν βασιλέων, τῆς τῶν πλοιζομένων σωτηρίας χάριν, ὥς φησιν ἡ ἐπιγραφή.
At the end of this island lies a rock surrounded by sea, on which there is a tower, many storeys high and marvellously fitted out in white stone, called by the same name as the island. Sostratus of Cnidus, who was a friend of the kings, built this tower to keep sailors safe, as the inscription says.