Temple C (dedicated to Herakles), is the earliest surviving temple on the acropolis, and it dates from the first half of the VI century. It was set on the highest point of the plateau and may have replaced an earlier sacred building. in plan it was very elongated, with 17 side columns, and a double, 6-column frontal colonnade. Some of these columns were of the early, monolithic type, while others were built up of drums; the number of flutes also varied. All these features signify that the building was continued over many years.
The upper structure was made of wood and decorated with terracottas, and a huge moulded terra-cotta mask of a gorgon decorated the centre of each pediment (see picture). Lion-head water-sprouts were also used here, and are among the earliest known.

Possibly this temple was used for storing the deeds of the Archives, for several hundred seals, probably originally affixed to papyrus documents or tablets, were discovered. These seals portrayed Herakles either taming the bull or with a dolphin and club.