(19th Mounykhion) This was a festival in honor of Olympian Zeus, but not related to the Games in Olympia. It was instituted by the sixth century tyrant Peisistratus and was associated with the inauguration of the temple of Olympian Zeus at Athens, which was not complete until Roman times. The festival included a procession of cavalry and, at least in Hellenic time, cavalry contests and exhibitions. Also, large numbers of bulls were sacrificed to Zeus (Adkins and Adkins 355; Campbell 285; Parke 144-5).
Adkins, Lesley and Roy A. Adkins, Handbook to Life in Ancient Greece, 1997
Campbell, Drew, Old Stones, New Temples, 2000
Parke, H.W., Festivals of the Athenians, 1977