Wales boasts a stunning array of castles, the most per square mile of any country in Europe, from the earliest stone fortifications at Chepstow to the 19th-century folly of Castell Coch and from the splendour of Caernarfon, Beaumaris, Conwy and Harlech, recognised as UNESCO World Heritage Sites, to the spectacular ruins of Carreg Cennen. This commemoration of a nation's architectural heritage tells the story of thirty-seven of these remarkable achievements.