How Medieval Builders Built Castles No Modern Architect Could Replicate

In 1078, a monk began a castle that still has not fallen.

His name was Gundulf, the Bishop of Rochester, and he was the best builder of his age. The castle was the great white keep at the heart of the Tower of London. Gundulf had no steel, no power tools, and no engineering degree. He had cut stone, burnt lime, a length of rope, and a craft passed from hand to hand. Nine and a half centuries later, his walls have never shifted, still square, still standing, still carrying their own weight without complaint.