Castles – citadels of world heritage. All over Europe, millions flock to see these masterpieces in stone.

They are drawn by the astonishing scale of construction – and by a sense of a lost world of heroism and chivalry. But castles are more than magnificent monuments to a past that’s dead and gone. They hold the key to understanding a crucial period in the growth of our civilisation.

In this video, we’ll see how some of the great castles of Europe were built, and how the ideas and techniques behind their construction changed and developed in a few short centuries. Kings and barons found the resources and manpower to start building castles, and spent fortunes on finishing them – and all of this happened at on a huge scale, at a frenetic pace, and often in the heart of hostile territory.

We’ll meet the Castle Builders – the labourers and masons who did the hard work; the geniuses of design who imagined them, the structural engineers who turned them into reality; and the kings and barons who commissioned them and lived in them.

We’ll travel from Richard the Lionheart’s astonishing Chateau Gauillard in Normandy to the ‘layered’ defences of Caerphilly – the first castle in Britain built to be defended by walls within walls – and around Edward I’s massive ‘ring of iron’ that gripped North Wales.

Large-scale dramatic reconstructions and state-of-the-art computer graphics will give us a thrilling sense of how all of these mediaeval mega-structures were designed and built.