The most important altar complex of the Sanctuary of Apollo belongs to the patron god and is located approximately in the centre of the Lower Terrace. The oldest altar is connected with the I Apollonion. Placed in front of the front of the temple, the altar does not follow its orientation and is not perfectly aligned with it. The structure consists of a long, narrow mensa with an api platform to the west, the prothysis. Towards the end of the 6th century BC, when a peristasis was added to the primitive oikos, a new altar was erected to the west of the first one.