Sillyon (Greek: Σίλλυον), also Sylleion (Σύλλειον), in Byzantine times Syllaeum or Syllaion (Συλλαῖον), was an important fortress and city near Attaleia in Pamphylia, on the southern coast of modern Turkey. The native Greco-Pamphylian form was Selywiys, possibly deriving from the original Hittite Sallawassi. Its modern Turkish names are Yanköy Hisarı or Asar Köy.[1]

Antiquity Throughout Antiquity, the city was relatively unimportant. According to one legend, the city was founded as a colony from Argos, while another holds that it was founded, along with Side and Aspendos, by the seers Mopsos, Calchas and Amphilochus after the Trojan War.[2] The city is first mentioned in c. 500 BC by Pseudo-Scylax (polis Sylleion). From 469 BC, the city (as Sillyon) became part of the Athenian-led Delian League. It is mentioned in the Athenian tribute lists in c. 450 BC and again in 425 BC, and then disappears again from the historical record until 333 BC, when Alexander the Great is said to have unsuccessfully besieged it. According to Arrian (Anabasis Alexandri I. 26), the site (recorded as Syllion) was well-fortified and had a strong garrison of mercenaries and “native barbarians”, so that Alexander, pressed for time, had to abandon the siege after the first attempt at storming it failed.[2]

The city was extensively rebuilt under the Seleucids, especially its theatre. In later times, when most of western Asia Minor fell to the Kingdom of Pergamon, Sillyon remained a free city by a decision of the Roman Senate.[2]