The Castle of the Knights of the Order of Saint John is situated at the entrance of Kos harbour and is an amazing place to visit. The sprawling ruins, some of which are extremely well-preserved, are located on what used to be an island and the bridge which once joined it to the mainland is still usable. Parts of the castle date back to the late 14th century but as it took over a hundred years to build there is evidence of more than one architectural style at the site. The castle has two defensive precincts: the interior has four circular corner towers and the larger exterior precinct has massive bastions in its four corners, battlements and gun ports. The two precincts are separated by a moat and joined by a drawbridge. There is a Hellenistic frieze over the main gate. A museum on the site, which is housed in a reconstructed building that was once the knights' warehouse, holds alters, sculptures and inscriptions from the site. The elevated sections of the castle afford visitors astounding views over the ocean. It is best to wear sensible walking shoes when visiting as exploring the castle thoroughly means traversing some steep steps and uneven ground.