Château de La Roche-Guyon, La Roche-Guyon

The Château de La Roche-Guyon is a rare hybrid of medieval fortress, troglodytic cave dwelling, and 18th-century aristocratic residence built into a chalk cliff overlooking the Seine valley. The original fortress was carved directly into the cliff face in the late 11th century to defend Île-de-France from Norman raids, with a 38-metre stone keep added on the hilltop around 1190 under Philippe Auguste. A secret underground passage of over 100 metres connects the hilltop keep to the lower manor through solid chalk.