The Dromos, or running surface of the stadium, was 600 ancient feet of hard packed yellow clay. The surface was prepared for competition by digging up this clay, then rolling it so as to form a hard crust over a softer substrate.
Below: Water channel and 200-ft marker
The track was marked every 100 feet by a small stone marker. Around the edges of the track, a water-channel of stone carried fresh water to thirsty athletes and spectators from a small spring (link) 500 meters away via a terracotta pipeline.
At both ends of the the track a balbis (above left), or starting line, was located. The balbis consisted of a line of stones with two toe grooves. In addition to the stone starting line itself, the balbis included a starting mechanism called a hysplex (above right), which functioned using the same torsion concept as a catapult. This mechanism allowed Greeks to have consistently fair starts to races.