The examples described above enable us to trace with some certainty the history of the Greek stadium. In its simplest form it is a long parallelogram, marked by two lines at either end. The spectators stand along the course on raised banks, natural or artificial. Stone seats occur first perhaps in the fifth century at Epidaurus. In the second half of the third century more elaborate stone seats appear near the centre of the course, which seems to have been usually the place of honour. The curved sphendone with its rows of seats does not appear till the Hellenistic period. Finally, when both ends are curved the stadium approaches the type of the Roman circus, and the resemblance is increased by the addition of colonnades either round the sphendone or round the whole course. The development of the actual racecourse is more rapid: the needs of competitors came before the needs of spectators. The starting lines and finish seem to have been first marked by pillars temporary or permanent on either side. These pillars exist at Epidaurus, and survive at a much later period in the Panathenaic stadium. Pillars are commonly represented in athletic scenes on fifth-century vases.[455] Often they are merely the shorthand symbol used by the vase-painter to denote the buildings of the gymnasium or palaestra. In foot-races and horse-races it is reasonable to suppose that they represent the pillars at the start or finish of the race. They occur chiefly on the red-figured vases, and the usual type is that of a fluted pillar often standing on a square basis. The starting lines with double grooves appear certainly in Macedonian times, though their introduction may well date back to the laying out of the stadia at Olympia and Delphi in the fifth century. The importance attached to the starting lines is proved by their frequent mention in inscriptions. Finally, in Roman times these starting lines were superseded by a row of pillars, between which was fixed some sort of barrier. The details and use of all these arrangements will be more conveniently discussed in connexion with the actual foot-race.