Condé Museum

The Chateau de Chantilly north of Paris was left to the nation in 1897 by Henri d'Orleans, Duke of Aumale, a son of the last French king, on one strict condition: the paintings must never leave the walls, and nothing may be rehung. So the Conde Museum is frozen as he arranged it in the 1890s, canvases stacked frame to frame in the crowded fashion of a private collector, not spaced out the way a modern gallery would.

What hangs there is the richest old-master collection in France outside the Louvre. The duke bought a small rotunda of Raphaels, Piero di Cosimo, Poussin, and a room he built for two panels by Jean Fouquet.

His greatest treasure is kept in the dark. The Tres Riches Heures, the most famous illuminated manuscript of the Middle Ages, painted for the Duke of Berry around 1410 with its calendar of peasants and castles, is far too fragile to display, so visitors see a facsimile while the original rests in the library. Because of the no-loan clause, it has almost never travelled.