Kos is one of the most popular Dodecanese islands, second only to Rhodes in visitor numbers. The main town, also called Kos, sits on the eastern tip of the island with a harbour dominated by the Castle of the Knights of St John. Despite the heavy tourist industry, the town has genuine historical depth — the ancient city's ruins spread through the centre, the Tree of Hippocrates stands in the main square, and the Asklepion, the most important medical school of antiquity, is just a few kilometres away.
The island is long and narrow, with a string of beaches along the north coast and quieter, wilder terrain in the interior. Kos Town is the base for most visitors; the resort strip extends west to Tigaki and Mastichari. For fewer tourists and better scenery, the mountain villages of Zia and Pyli and the far western bay of Kefalos are worth the effort. The island is flat enough to explore entirely by bicycle, which is how the more discerning visitors get around.