Panionium

The Panionium (Ancient Greek: Πανιώνιον, Paniōnion) was an Ionian sanctuary dedicated to Poseidon Helikonios and the meeting place of the Ionian League. It was on the peninsula of Mt. Mycale, about 100 kilometres (62 mi) south of Smyrna—now İzmir, in Turkey. Herodotus describes it as follows:The Panionion is a sacred ground in Mykale, facing north; it was set apart for Poseidon of Helicon by the joint will of the Ionians. Mykale is a western promontory of the mainland opposite Samos; the Ionians used to assemble there from their cities and keep the festival to which they gave the name of Panionia.