The ruined Chateau d'Epinal stands above the old town in a broad public park. There is not a polished chateau interior to tour; the pleasure is the climb, the fragments of wall, and the view over the Moselle valley.
Come late in the afternoon if the weather is clear. The park is also a good place to reset after the museums, with shaded paths, open lawns, and enough height to make sense of Epinal's position at the edge of the Vosges.