Passage 6.21.9
προελθόντι δὲ οὐ πολὺ γῆς χῶμά ἐστιν ὑψηλόν, τῶν μνηστήρων τῶν Ἱπποδαμείας τάφος. Οἰνόμαον μὲν οὖν ἐγγὺς ἀλλήλων κρύπτειν γῇ φασιν οὐκ ἐπιφανῶς αὐτούς· Πέλοψ δὲ ὕστερον μνῆμα ἐν κοινῷ σφισιν ἐπὶ μέγα ἐξῆρε τιμῇ τῇ ἐς αὐτοὺς καὶ Ἱπποδαμείας χάριτι, δοκεῖν δέ μοι καὶ ὑπόμνημα ἐς τοὺς ἔπειτα ὅσων τε καὶ οἵων τὸν Οἰνόμαον κρατήσαντα ἐνίκησεν αὐτός.
After advancing a short distance, there is a high earthen mound, the tomb of the suitors of Hippodameia. Now, they say that Pelops originally buried them close together and without distinction, but later on he raised a great memorial mound in honor of them collectively, through respect for the suitors themselves and favor for Hippodameia—though it seems to me also as a reminder to posterity of how many and how notable were the men whom he himself surpassed by defeating Oinomaos.