We’ve stayed at the Belladone site ( before we got our Cali). I agree it’s a great base for doing some of the iconic Tour climbs. It’s a the very bottom of the Croix de Fer and just down the valley from Alpe D’Huez. We cycled both of the these as well as the Galibier, Les Deux Alpes and the Col D’Ornon. It’s about 4 miles from Bourg D’Oisans and about 25 miles from Grenoble.