Go to Marly-le-Roi
Marly is not the place to visit if you are feeling blue, it feels sad, just the bare bones of what it once was. But do not leave it off your itinerary as you can still imagine the beauty and former importance of the parc with its strong axes that project to the suburbs of Paris. The parc now comes under Versailles and there are plans for a restoration of sorts. More 'interpretation' material in the parc would be useful and so would car and coach parking signs but small problems.
If it rains you won't need an umbrella as 'the rain never wets at Marly'.