The Seventeen Towers of the Château d'Angers
Angers, rebuilt in the 1230s for the French crown: seventeen round towers in banded schist and limestone, set into a curtain wall on a rock above the Maine. Round towers have no blind corner and cannot be undermined at an angle, which is precisely why square ones stopped being built.
Thirteenth-century castle building in France was a state programme, not a private one. Philip Augustus and then Louis IX standardised a form — circular donjon, round flanking towers, arrow loops covering every face — and repeated it across newly annexed territory. It was expensive in iron as much as stone: cramps, tie bars, portcullis mechanisms, hoardings and the tools to cut the masonry. See iron and innovation in thirteenth-century French castle architecture.
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