Question: Jennifer Pharr Davis has hiked on the long-distance walk in Europe around Mont Blanc that covers approximately what distance?
Context: Courmayeur is a town and "comune" in northern Italy, in the autonomous region of Aosta Valley.  At an elevation of 1224 m above sea level, it is located at the foot of the southern side of Mont Blanc, at 4810 m the highest point in the Alps and western Europe (see Seven Summits), and is crossed by the Dora Baltea river.  Courmayeur shares administration of Mont Blanc with its neighboring commune of Saint-Gervais-les-Bains in France, and is consequently able to claim the title of highest commune in Italy.  Courmayeur also shares access to the glacial ski run of the "Vallée Blanche" with another French town, Chamonix, which sits at the opposite, northern, side of the Mont Blanc massif. The Mont Blanc Tunnel is a highway tunnel in Europe, under the Mont Blanc mountain in the Alps.  It links Chamonix, Haute-Savoie, France with Courmayeur, Aosta Valley, Italy, via European route E25.  The passageway is one of the major trans-Alpine transport routes, particularly for Italy, which relies on this tunnel for transporting as much as one-third of its freight to northern Europe.  It reduces the route from France to Turin by 50 km and to Milan by 100 km .  Northeast of Mont Blanc's summit, the tunnel is about 15 km southwest of the tripoint with Switzerland, near Mont Dolent. Refugio Elisabetta (or Refugio Elisabetta Soldini Montanaro to give it its full, but less well-used name) is a refuge in the Italian Alps at an altitude of 2,195 m, which provides a convenient overnight stage for walkers undertaking the Tour du Mont Blanc.  It is located 3 km north-east of the Col de la Seigne, at the south-west end of the Mont Blanc massif, and provides good views of Mont Blanc and the Aiguille Noire de Peuterey.  Because of its popularity, plus the fact that there are no other huts along this part of the Tour du Mont Blanc, walkers are advised to book in advance during the peak periods in July and August. The Vallot Hut (French: "Refuge Vallot") is a refuge in the Mont Blanc massif on the upper slopes of Mont Blanc in the Alps.  It is located below the Bosses Ridge between the Dome du Gouter and Mont Blanc summit, at an altitude of 4,362 metres.  Intended only as an emergency shelter, and not as a base for ascending Mont Blanc, this unheated duralumin box was designed to accommodate up to 12 people, but often contains considerably more. The Grands Mulets Hut (French: "Refuge des Grands Mulets") is a mountain refuge in the Mont Blanc massif in the French Alps at an altitude of 3,051 m.  It is owned by the Club Alpin Francais.  The hut is located on a pyramidal rock island, at the junction of two streams of the Bossons Glacier on the north side of Mont Blanc.  If the state of the glacier is not too severe, the hut is wardened in summer and can be used as an alternative route of ascent to the summit of Mont Blanc, following the original historic route by the first ascensionists.  Nowadays the hut is used more frequently by ski-mountaineers in spring, or as a more sheltered and alternative route of descent from Mont Blanc than the much more popular Gouter route, though route-finding can be difficult in fog and requires prior knowledge of the crevassed state of the Bossons glacier below the hut. The Tour Ronde (3,792 m) is a mountain in the Mont Blanc massif of the Alps, situated on the border between France and Italy.  It is a prominent mountain, some 3.5 km north-east of Mont Blanc, but is effectively part of a continuation of the south eastern spur of Mont Maudit (l'Arete de la Brenva) which forms a frontier ridge between the two countries.  It is easily accessible to mountaineers and provides not only a very good viewpoint from its summit of the Brenva face and the major peaks on the southern side of Mont Blanc, but it also offers a popular introduction to alpine climbing of all grades, including a north face ascent. The Tour du Mont Blanc or TMB is one of the most popular long-distance walks in Europe.  It circles the Mont Blanc massif, covering a distance of roughly 170 km with 10 km of ascent/descent and passes through parts of Switzerland, Italy and France. Jennifer Pharr Davis is an American long distance hiker, author, speaker, National Geographic Adventurer of the Year, and Ambassador for the American Hiking Society.  She has hiked over 12,000 miles on six different continents, including thru-hikes on the Pacific Crest Trail, the Appalachian Trail (three times), the Colorado Trail, the Long Trail in Vermont, the Bibbulmun Track in Australia, and numerous trails in Europe and South America (e.g., the Tour du Mont Blanc, West Highland Way, Laugavegur, GR 11 (Spain), GR 20, and the Pembrokeshire Coast Path, Cotahuasi Canyon and the Inca Trail to Machu Picchu). The Tête Rousse Hut (French: "Refuge de Tête Rousse") is a mountain hut in the Mont Blanc massif in the French Alps.  It is located beside the Tête Rousse Glacier at an altitude of 3,167 m. Owned by the Club Alpin Francais (CAF), it is normally reached after a multi-hour climb from Nid d'Aigle, the highest stop on the Mont Blanc Tramway.  It is commonly used by mountaineers attempting to climb the normal (Gouter route) to the summit of Mont Blanc.  Staying here, rather than continuing to the higher Gouter Hut adds an extra 2–3 hours to the ascent of Mont Blanc, but is less cramped than the latter and also avoids having to climb the dangerous 'Grand Couloir' later in the day when the risk of injury from stonefall is at its greatest. Storm over Mont Blanc (German: "Stürme über dem Mont Blanc" ) is a 1930 German film written and directed by Arnold Fanck and starring Leni Riefenstahl, Sepp Rist and Ernst Udet.  The film is about a man who works alone at the Mont Blanc weather station gathering data.  His only contact with the world below is via Morse code signals.  He is joined by a woman friend, who helps him survive a terrible storm over the mountain.  Filmed on location in Arosa, Switzerland, Babelsberg Observatory in Potsdam, Germany, and Mont-Blanc in Chamonix, France, the film is notable for its dramatic mountain footage and depictions of a violent snow storm.  "Storm over Mont Blanc" premiered in Dresden, Germany on 25 December 1930.
Answer: 170 km