The black-graded Sarenne run drops from the Pic Blanc at 3,330 metres all the way down to the bottom of the Sarenne gorge — vertical drop of about 1,800 metres. The top section is genuinely steep and exposed, often with hard wind-scoured snow; the long middle and bottom sections are easier cruising through a wild glacial valley with no lift infrastructure in sight.
Take the Pic Blanc cable car early on a clear day. The descent is around 90 minutes for a competent skier including stops to admire the view (which on a good day extends to Mont Blanc). At the bottom you ride the Chalvet and Alpauris lifts back to the resort.