Passage 5.15.3
ἔστι δὲ ἐν τῇ Ἄλτει τοῦ Λεωνιδαίου περᾶν μέλλοντι ἐς ἀριστερὰν Ἀφροδίτης βωμὸς καὶ Ὡρῶν μετʼ αὐτόν. κατὰ δὲ τὸν ὀπισθόδομον μάλιστά ἐστιν ἐν δεξιᾷ πεφυκὼς κότινος· καλεῖται δὲ ἐλαία Καλλιστέφανος, καὶ τοῖς νικῶσι τὰ Ὀλύμπια καθέστηκεν ἀπʼ αὐτῆς δίδοσθαι τοὺς στεφάνους. τούτου πλησίον τοῦ κοτίνου πεποίηται Νύμφαις βωμός·
In the Altis, as you are about to pass beyond the Leonidaeum, there stands on your left an altar to Aphrodite, and after it one to the Horae. Also, by the rear chamber of the temple, there grows a wild olive tree especially on the right side. This olive tree is called "Kallistephanos" ("Beautiful-crowned"), and it is from this tree that crowns are ordained to be awarded to victors in the Olympic games. Near this wild olive a second altar has been dedicated to the Nymphs.