Question: Refuge Robert Blanc is a refuge in the Alps located on the route of a popular walk that is roughly how long?

Context paragraphs:
Refuge du Théodule: Refuge du Théodule is a refuge in the Pennine Alps located at the Theodulpass between the Mattertal and Valtournanche in the Aosta Valley, Italy.

Refuge Robert Blanc: Refuge Robert Blanc is a refuge in the Alps at an altitude of 2,750 m, located on the route of the Tour du Mont Blanc.

Refuge du Promontoire: Refuge du Promontoire is a refuge in the Alps located in France in the massif des Ecrins, it is just build on rock in front of the South face of La Meije.  It's the starting point of the famous crossing of La Meije, which is known to be one of the most beautiful mountain run into the Alps.

Tour du Mont Blanc: 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.

Grands Mulets Hut: 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.

Torino Hut: The Torino Hut (Italian: "Rifugio Torino" ; French: "Refuge Torino") is a high mountain refuge in the Alps in northwestern Italy.  Located near the border with France, it is about 15 km southwest of Mont Dolent, the tripoint with Switzerland.  The refuge is in the Mont Blanc massif above the town of Courmayeur in the Aosta Valley, Italy.  It can be most easily accessed from the Italian side by the Skyway Monte Bianco cable car from La Palud in Courmayeur, with a change at the Pavilion du Mont Fréty.  It can also be reached from Chamonix via the Aiguille du Midi, either by cable car which crosses the massif, or by a long crossing of the Glacier du Gèant.  The refuge lies nearly directly above the 11.6 km Mont Blanc Tunnel, which passes deep underground, and connects Courmayer to Chamonix.

Refuge du Cuchet: Refuge du Cuchet is a French refuge in the Alps located in Vanoise National Park, Savoie.

Vallot Hut: 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.

Grison Alps: The Grison Alps are the mountains of the Graubünden canton of Switzerland (Grisons being the English name for the Graubünden region).  There are many significant peaks in the Grison Alps, including the Tödi (3,614 m) and the highest peak, Piz Bernina (4,049 m).  Many of the mountain ranges feature extensive glaciers, such as at the Adula, the Albula, the Silvretta, the Bernnina or the Rätikon range.  The Grison Alps include parts of both the Eastern Alps and the Western Alps.  The Eastern Alps located in Graubünden are the Rhaetian Alps, which is part to the Central Eastern Alps.  The Rhaetian Alps consists of the following mountain ranges: Samnaun Alps, Rätikon, Silvretta, Sesvenna Range, Albula Range, Plessur Range, Oberhalbstein Range, Livigno Range, Bregaglia Range and the Bernina Range.  The Western Alps located in Graubünden, include portions of the Lepontine Alps and the Glarus Alps.

Gonella Hut: The Gonella Hut (French: "Refuge Francesco Gonella"; Italian: "Rifugio Francesco Gonella" and sometimes called "Rifugio del Dôme"; or "Refuge du Dôme") is a high altitude mountain hut in the Aosta Valley in the Mont Blanc massif area of the Alps.  It lies at an altitude of 3071 metres, above Val Veny near Courmayeur in Italy.  The refuge is located on the Italian 'normal route' to Mont Blanc.

Supporting paragraphs: Refuge Robert Blanc Tour du Mont Blanc
Answer: 170 km