The main port and population centre on the island, also called Kos, is also the tourist and cultural centre, with whitewashed buildings including many hotels, restaurants and a small number of nightclubs forming the famous Kos town "barstreet". The town has a 14th century fortress at the entrance to its harbour, erected in 1315 by The Knights of Saint John of Rhodes.
The ancient physician Hippocrates is thought to have been born on Kos, and in the center of the town is the Plane Tree of Hippocrates, a dream temple where the physician is traditionally supposed to have taught. The limbs of the now elderly tree are supported by scaffolding. The small city is also home to the International Hippocratic Institute and the Hippocratic Museum dedicated to him. Near the Institute are the ruins of Asklepieion, where Herodicus taught Hippocrates medicine. Kardamena is a popular resort for young British holidaymakers and has a large number of bars and nightclubs