Castle Builders unearths the human story of those who laboured to build these massive fortresses - and the visions of the royals and aristocrats that invested stupendous sums to buttress their power and glorify their courts.
Across Europe, from Carcassonne to Caerphilly, from the Rhine to the Thames, masterpieces in stone draw visiting tourists in the millions.
With towering walls and rolling turrets, these long-standing survivors of military history provide us with some of the most breathtaking images of recent European civilisation.
But how were these medieval super-structures built? How were revolutionary machines alongside countless men and women organised to create such colossal fortifications built not only for defence but also for beauty?