There may not be a better base in the French Alps for cycling than Barcelonnette. Located in the Ubaye valley (south alps), it is literally surrounded by mountains looking to be climbed. The town is at 1,135 metres (3,720 feet) – so even the easier climbs are tougher near the oxygen starved top. Here is a link to a PDF brochure from the local tourist office. It is in French but from page 20, the Cycling maps and routes are easy to understand.