Exposed by a devastating earthquake in 1933, Kos’ ancient centre occupies a vast area south of the castle. Back in the 4th century BC, this was the first town ever laid out in blocks, and you can still discern the original town plan, even though it’s very overgrown. Landmarks include a massive columned stoa and the ruins of a Shrine of Aphrodite, Temple of Hercules and Christian basilica.
The site is fenced, but usually open all day. Locals use it as a shortcut.