The Xystos , 3D reconstruction
© Ephorate of Antiquities of Phocis, Ministry of Culture and Sports

On the upper terrace stood the xystos, a covered portico measuring 9.05 by 185.95 meters. This was the length of a Pythic stadium. Its portico comprised two successive colonnades, consisting of 83 columns: the earlier one, built in the Doric order in the 4th century B.C., was made of poros stone; it was replaced, however, in the Roman period by another, marble one, of the Ionic order. The floor of the xystos was covered with sand for facilitating the athletes, who practiced there when the weather conditions didn't allow them to use the open track, the paradromis.

Text - Translation:Dr. Aphrodite Kamara, Historian