Passage 6.20.8
ἔστι δὲ ἐπὶ τῷ πέρατι τῶν ἀγαλμάτων ἃ ἐπὶ ζημίαις ἐποιήσαντο ἀθλητῶν, ἐπὶ τούτῳ τῷ πέρατί ἐστιν ἣν Κρυπτὴν ὀνομάζουσιν ἔσοδον· διὰ δὲ αὐτῆς τούς τε Ἑλλανοδίκας ἐσιέναι ἐς τὸ στάδιον καὶ τοὺς ἀγωνιστάς. τὸ μὲν δὴ στάδιον γῆς χῶμά ἐστι, πεποίηται δὲ ἐν αὐτῷ καθέδρα τοῖς τιθεῖσι τὸν ἀγῶνα. ἔστι δὲ ἀπαντικρὺ τῶν Ἑλλανοδικῶν βωμὸς λίθου λευκοῦ·
At the end of the statues which were set up as penalties against athletes, there is an entrance called the Hidden Gate. Through this entrance, the judges of the Greeks and the competitors pass into the stadium. The stadium itself is an earthen embankment, and within it is a seat constructed for the presidents of the contests. Opposite the judges' seats stands an altar of white stone.