Passage 6.20.11
ἑκατέρα μὲν δὴ πλευρὰ τῆς ἀφέσεως πλέον ἢ τετρακοσίους πόδας παρέχεται τοῦ μήκους, ᾠκοδόμηται δὲ ἐν αὐταῖς οἰκήματα· ταῦτα τὰ κλήρῳ τὰ οἰκήματα διαλαγχάνουσιν οἱ ἐσιόντες ἐς τὸν ἀγῶνα τῶν ἵππων. πρὸ δὲ τῶν ἁρμάτων ἢ καὶ ἵππων τῶν κελήτων, διήκει πρὸ αὐτῶν καλῴδιον ἀντὶ ὕσπληγος· βωμὸς δὲ ὠμῆς πλίνθου τὰ ἐκτὸς κεκονιαμένος ἐπὶ ἑκάστης Ὀλυμπιάδος ποιεῖται κατὰ τὴν πρῷραν μάλιστά που μέσην, ἀετὸς
Each side of the starting-place is over four hundred feet in length, and buildings stand along them. These buildings are assigned by lot to those who enter horses for competition. Before the chariots or the riding-horses there runs a cord instead of a barrier. An altar of unbaked brick, coated on the outside with plaster, is made at each Olympiad near the very middle of the front; an eagle is placed upon it.