The Asklepion, the most famous monument on the Greek island of Kos, stands on a low hill overlooking the sea. The site, now mostly in ruins, was used as a centre of healing and worship from the 4th c. BC. The earliest part of the temple was dedicated to the healer-god Asklepios. Here the sick slept, in the priests' quarters, next to the entrance to an underground spring, and waited for Asklepios to appear to them in their dreams and heal them.