Kos Town has more historical depth than its mass-tourism reputation suggests. The Knights of St John Castle dominates the harbour, the ancient Agora ruins spread out behind the main street, and the Tree of Hippocrates — supposedly the plane tree under which the father of medicine taught — stands in the Plateia Platanou, although the current tree is only about 500 years old and Hippocrates died around 370 BC.
The real highlight is the Asklepion, the ancient healing sanctuary dedicated to Asclepius (god of medicine) and the most important medical school of antiquity. It sits on a hill 4 km from town with good views toward Turkey. Inland, the mountain villages of Zia and Pyli offer a quieter, less commercial face of the island.