Ayasuluk is the low hill in the middle of Selçuk town, with the Byzantine fortifications crowning the top and the Basilica of St John spread across the southern slope. Excavations have shown that the hill was occupied continuously from the Bronze Age (around 2000 BC) through to the early Ottoman period — making it one of the longest-inhabited spots in this part of Anatolia.
The Byzantine castle at the summit is open at the same hours as the basilica and is included on the same ticket. It is not much more than walls and a few rebuilt towers, but the climb is short and the panorama from the top — over the basilica, the mosque, the temple, and across to Ephesus — is the reason to do it.