Kos, Greece

Kos is the main town on the Dodecanese island of the same name, sitting roughly four kilometres off the Turkish coast and home to about 35,000 residents. It is recognised as the birthplace of Hippocrates, the physician born around 460 BC who is regarded as the father of medicine, and a 12-metre plane tree in the centre is traditionally said to mark the spot where he taught. A dense archaeological zone surrounds the harbour, including the 3rd-century-BC Ancient Agora, the Casa Romana (a 3rd-century Roman villa) and the 14th-century Castle of the Knights of Saint John. Each site sits within walking distance of the next, layering Greek, Roman and medieval remains across a compact modern town. How those layers fit together becomes clearer once you trace them street by street.