The hippodrome was situated at the south-east corner of the sanctuary of Olympia, on the large flat area south of the stadium and ran almost parallel to the latter. Its exact location is unknown, since it was washed away completely by the Alpheios river in the Middle Ages when the river's west bank dike fell into disrepair. The hippodrome housed the equestrian contests (horse racing and chariot-racing) of the Olympic Games and was therefore one of the most important monuments of the site.
Pausanias, who visited Olympia in the second century BC, describes the monument (VI, 20, 10-21) as a large, elongated, flat space, approximately seven hundred and eighty metres long and three hundred and twenty metres wide (four stadia long and one stade four plethra wide, according to Pausanias). The elongated racecourse was divided longitudinally into two tracks by a stone or wooden barrier, the embolon. All the horses or chariots ran on one track towards the east, then turned around the embolon and headed back west. Distances varied according to the event. The racecourse was surrounded by natural (to the north) and artificial (to the south and east) banks for the spectators; a special place was reserved for the judges on the west side of the north bank.
The architect Agnaptos built a portico, no traces of which survive, on the west side of the racecourse. Here the hippaphesis, an ingenious starting gate invented by the sculptor Cleoitas and described in detail by Pausanias, was installed. The starting point had the shape of an isosceles triangle, with a built compartment for each horse or chariot. At the apex of the triangle was a bronze dolphin, and at its base, opposite the Agnaptos portico, an altar with a bronze eagle on top and the gate's mechanism hidden inside. The mechanism was probably operated by a single person. In front of the horses were ropes that kept them from starting. During the hippaphesis, the ropes were gradually released starting with those of the horses in the back while the dolphin began to descend and the eagle was raised. When the horses or chariots reached the same point at the base of the racetrack, and the eagle was visible to all the spectators, the trumpets sounded and the race began. Near the starting point was the statue of Hippodameia, which held the victor's head-band, and at the south-east end of the hippodrome a circular altar dedicated to the deity Taraxippos, the horse rouser.