Montfort-L'amaury is one of the most beautiful village of Paris's country-side. You can walk from the house, say hello to the horses over a walkers only pathway and reach the central place with good bakeries, butchers, "cafés", and many artisans or small shops. But you also can take the bikes and ride across the Rambouillet's forest in which you can ride during a full day without going back on your steps (there's even a lake and a beach!).
And oc, you're 40min away from Paris.