PANIONION is located on the northern slope of Mount Mycale (Samson Mountain), facing the island of Samos, where the famous Battle of Mycale between the ancient Greeks and Persians took place. Its ruins are located on the western slope of Otomatik Hill within the borders of present-day Güzelçamlı.
In the 7th century BC, the Ionians formed a federation of 12 city-states. The delegates of this federation met at regular intervals in Güzelçamlı, known as "Panionion", to make important decisions about the future, strength, and influence of the federation.
In excavations carried out in 1957-58 by Professor Gerhard Kleiner, an archaeologist from the University of Frankfurt, a structure in the form of an ancient theater with 11 steps carved into the rock face was discovered. Kleiner proved that this was the center of Panionion and that there was an altar dedicated to Poseidon Helikonios. It is stated that the Panionian festivals were celebrated here during the Ionian period.