Corot, a tireless traveller, visits the Oise region and stops on the road to Villers-Cotterêts.  He paints the foothills in the Pierrefonds area dominated by the ruins of the fortress, silhouetted against the foliage of the forest of Compiègne.  Rejecting a romantic dramatisation, his work is a carefully balanced construction, based on a few luminous strokes and on the superposition of coloured background, giving the work a look of modernity.  The comment on this masterpiece, in the 1873 catalogue of the collection, states: « unfinished ».