The simplest of all Greek stadia was that at Olympia, and it retained its simplicity throughout its history.[435] We have seen that before the middle of the fifth century all the games were held in the plain commanded by the treasury terrace, and that the permanent running track was first constructed about 450 B.C., after the completion of the first eastern colonnade. At this date the ground at the foot of the hill of Cronus was levelled so as to form a parallelogram some 212 metres long by 29 broad, somewhat broader, however, at the centre than at the ends. This parallelogram was enclosed by a stone sill, and within this sill at a distance of about a metre ran an open stone gutter, opening at regular intervals into stone basins. This gutter, fed from the conduit which ran along the foot of the treasury steps, provided competitors and spectators with the water which they must have sorely needed, exposed as they were all day long, without protection, to the parching rays of the summer sun. The running track lay some 10 feet below the level of the Altis, and slightly below the level of the surrounding plain which sloped gradually upwards to the south towards the bank of the Alpheus. The only accommodation for spectators was afforded by the slopes of the hill of Cronus and this open plain, which it has been calculated would have accommodated from 20,000 to 30,000 people. At a later date, possibly after the battle of Chaeronea in 338 B.C., the ends and southern slope were raised by an artificial embankment. This embankment extended to the south some 40 metres from the actual track, and on it some 40,000 or 45,000 spectators could find standing room. The ends of the embankment were straight, there was no curved theatre or σφενδόνη, nor during the whole history of the stadium did any seats exist. Seats, probably of wood, were provided for a few privileged officials, but the spectators stood or reclined on the banks. At the north-west corner of the stadium a postern gate communicated with the Altis by means of a tunnel through the embankment, which in Roman times was roofed with a stone vault. This was the secret entrance reserved for officials and competitors.[436] The spectators found their way into the stadium over the embankments or along the slopes of Mount Cronius. [Illustration: Fig. 41. Portion of starting lines at Olympia.]