The concentric castle — two complete rings of defensive walls, one inside the other — is the most sophisticated form of medieval European fortification. Where it came from, why it worked, and the great surviving examples.
The middle Rhine gorge between Bingen and Koblenz holds the densest concentration of medieval castles in Europe — a UNESCO World Heritage landscape of river, vineyard, and stone towers.
The greatest concentration of Renaissance chateaux in the world — from Chambord's 440 rooms to Chenonceau spanning the Cher, the Loire valley defines French castle architecture.
