Monte Viso (3,841m) sits just on the Italian side of the border, but it dominates the skyline of the eastern Queyras. Walking trails from Abriès and from the Refuge du Viso get you close enough to feel its scale.
For serious walkers, the Tour du Mont Viso is a multi-day circuit around the mountain, with refuges on both sides of the border. The walk to the source of the Po, just below the peak, is a one-day target from the French side.