The Lacs de la Pra are a smattering of tiny lakes in the Belledonne mountain range, a western section of the Alps. And what a section.
My personal outdoor-exercise drug of choice: mountains.
The three-viewpoint ascent of La Bastille (big hill), Mont Jalla (about 600 m), and Mont Rachais (about 1000 m) is one pretty-much continuous climb suited to shorter, colder day
A relatively sporty day hike without too much transportation hassle