Serre-Chevalier is not a single village so much as a long, high Alpine playground in the Guisane valley. It runs from the fortified town of Briancon through Chantemerle and Villeneuve to Le Monetier-les-Bains, with ski lifts climbing the sunny slopes above the valley and the wild edge of the Ecrins close by.
In winter, the reason to come is the Serre Chevalier ski area: a big, linked domain of high runs, larch forest pistes, and enough terrain that intermediate skiers can roam for days. In summer the valley turns toward hiking, mountain biking, white-water sports, and road cycling, especially the hard climb to the Col du Granon.
The place has a softer side too. Les Grands Bains du Monetier gives the upper valley proper thermal-bath character, and Briancon's walls remind you that this has long been a frontier valley, not just a lift system. Serre-Chevalier is best if you want mountain days with a little more local texture than a purpose-built resort.