The Northern Limestone Alps are separated from the Central Eastern Alps by the Grauwacken Zone. However, the geologic subdivision, based on tectonics, suggests a different system: The Helvetic system in the north (including the Jura mountains, which do not geographically belong to the Alps), the Penninic system: mainly Central Alps (Engadine and "Tauern window") and Flysch Alps, the Austroalpine system: Northern Limestone Alps, Graywacke-Schist zone, Central Crystalline, the Southern Alps (Southern Limestone Alps and other chains south of the Periadriatic Seam) south of a huge geologic fault ("alpine-dinaric seam") parts of the Dinarides. Western Alps The Western Alps are commonly subdivided into the following: Ligurian Alps (from Savona to Colle di Tenda) Maritime Alps (from Colle di Tenda to Colle della Maddalena) Cottian Alps (from Colle de la Maddalena to Montgenevre Pass) Dauphiné Alps (from Col du Mont Genevre to Col du Mont Cenis) Graian Alps (from Col du Mont Cenis to the Col Ferret) Chablais Alps (from Lake Geneva to the Col des Montets) Pennine Alps (from Col Ferret to the Simplon Pass) Lepontine Alps (from Simplon Pass to Splügen Pass) Bernese Alps (north of the Rhône to the Grimsel Pass) Urner Alps (from Grimsel Pass to the Reuss) Glarus Alps (north-east of Oberalp Pass) Appenzell Alps (north of Sargans) Within the Eastern Alps, the most widely used subdivision is the Alpine Club's 1984 classification, which divides the region into about seventy small areas. Main chain The "main chain of the Alps" follows the watershed from the Mediterranean to the Wienerwald, passing over many of the highest and most famous peaks in the Alps. The most important passes and peaks which it crosses are given below (mountains are indented, passes unindented). From the Colle di Cadibona to Col de Tende it runs westwards, before turning to the north-west and then, near the Colle de la Maddalena, to the north. Upon reaching the Swiss border, the line of the main chain heads approximately east-north-east, a heading it follows until its end near Vienna. Colle di Cadibona (Italy, 435 m) Colle di Tenda / Col de Tende (France / Italy, 1908 m) Colle della Maddalena / Col du Larche (France / Italy, 1994 m) Monte Viso (France / Italy, 3841 m) Col de Montgenèvre (France / Italy, 1854 m) Col de Fréjus (France / Italy, 2537 m) Col du Mont Cenis (France, 2084 m) Aiguille de la Grande Sassière (France /