The ski resorts of Candanchú and Astún, high up near the French border, come alive during the winter-sports season from December to March/April.
Astún's Telesilla Truchas chairlift operates in July and August, giving access to day walks around mountain lakes either side of the French border.
Candanchú is on the long-distance GR11 walking trail, a day's walk across mountain passes from A Mina at the top of the Valle de Hecho (west) or Sallent de Gállego in the Valle de Tena (east).
Valle de Izas
There are beautiful summer day walks in side valleys including the Valle de Izas east of Canfranc-Estación; the tourist office has information. Walking right up to the Collado de Izas pass and back is an undertaking of about seven hours with 1000m of ascent and descent, but there are numerous shorter options. (And you can drive the first 2km up an unpaved road as far as the Fuerte de Coll de Ladrones, an abandoned fort.)