Lake Geneva is the largest body of water in Switzerland, and greatly exceeds in size all others that are connected with the main valleys of the Alps. It is in the shape of a crescent, with the horns pointing south, the northern shore being , the southern shore in length. The crescent form was more regular in a recent geological period, when the lake extended to Bex, about south of Villeneuve. The detritus of the Rhône has filled up this portion of the bed of the lake, and it appears that within the historical period the waters extended about beyond the present eastern margin of the lake. The greatest depth of the lake, in the broad portion between Évian-les-Bains and Lausanne, where it is just in width, has been measured as , putting the bottom of the lake at above sea level. The lake's surface is the lowest point of the cantons of Valais and Vaud. The culminating point of the lake's drainage basin is Monte Rosa at 4,634 metres above sea level.