The Ariege is a haven for outdoor mountain activities. The walking and trekking options are almost endless, and whilst there are not the highest Pyrenean peaks in this region, there are some stunning routes that keen walkers would be foolish to miss. One advantage of the Ariege is that the road network goes fairly high, allowing people to walk to the highest peaks in a day trip. There are some good guide books available eg 'L'Ariege... a pied' which you can buy locally and costs about 12 euros. The GR10 also runs through Ariege, as well as the Chemin de Bonnes Hommes and many others. For those who want to explore the area with an English speaking guide, you might try (http://www.marmot-tours.co.uk) as they organise week long group holidays in the area. They cover different levels of walking, plus other activity holidays such as mountain biking, road biking and cross country skiing in the winter.
For cyclists among you, the Tour de France come to Ariege almost every year. This year Stage 15 ended up at the Plateau de Beille, an infamous 16 km climb from the village of Les Cabannes up to what is a fantastic cross country ski station in the winter, and a great place for some walking in the summer. At 1800 m it has fabulous views of the Andorran / French border mountains and in summer is normally a fantastic temperature a few degrees cooler than the valley. There are numerous other cols for cycling up for keen road cyclists.
Cross country skiers are spoilt with a choice of two ski stations, the one at Plateau de Beille 60 km of pistes and the Domaine du Chioula another 50 km or so of tracks. The altitude of Beille means that it has an excellent snow record.