Château de Pierrefonds, France

Massive round towers with machicolated tops and pointed caps, seen from below the ramparts at Pierrefonds, on the edge of the Compiègne forest north of Paris. It looks like the perfect medieval castle because it was rebuilt to be one. The castle was a ruin when Napoleon III asked the architect Eugène Viollet-le-Duc to restore it in 1857. The outside follows medieval models closely, but much of the interior was his own invention, and work stopped after the emperor fell in 1870, leaving some rooms undecorated. The result is a nineteenth-century idea of the Middle Ages in solid stone, which is why film and television crews keep coming back: it stood in for Camelot in the BBC series Merlin.