Strabo Geography 4.6.6

[6] On the opposite side of the mountains, sloping towards Italy, dwell the Taurini, ¹ a Ligurian nation, together with certain other Ligurians. What is called the land of Ideonnus ² and Cottius belongs to these Ligurians. Beyond them and the Po are the Salassi; above whom in the summits [of the Alps] are the Kentrones, the Catoriges, the Veragri, the Nantuatae, ³ Lake Leman, ⁴ traversed by the Rhone, and the sources of that river. Not far from these are the sources of the Rhine, and Mount Adulas, ⁵ from whence the Rhine flows towards the north; likewise the Adda, ⁶ which flows in an opposite direction, and discharges itself into Lake Larius, ⁷ near to Como. Lying above Como, which is situated at the roots of the Alps, on one side are the Rhaeti and Vennones towards the east, ⁸ and on the other the Lepontii, the Tridentini, the Stoni, ⁹ and numerous other small nations, poor and addicted to robbery, who in former times possessed Italy. At the present time some of them have been destroyed, and the others at length civilized, so that the passes over the mountains through their territories, which were formerly few and difficult, now run in every direction, secure from any danger of these people, and as accessible as art can make them. For Augustus Caesar not only destroyed the robbers, but improved the character of the roads as far as practicable, although he could not every where overcome nature, on account of the rocks and immense precipices; some of which tower above the road, while others yawn beneath; so that departing ever so little [from the path], the traveller is in inevitable danger of falling down bottomless chasms. In some places the road is so narrow as to make both the foot traveller and his beasts of burden, who are unaccustomed to it, dizzy; but the animals of the district will carry their burdens quite securely. These things however are beyond remedy, as well as the violent descent of vast masses of congealed snow from above, capable of overwhelming a whole company at a time, and sweeping them into the chasms beneath. Numerous masses lie one upon the other, one hill of congealed snow being formed upon another, so that the uppermost mass is easily detached at any time from that below it, before being perfectly melted by the sun.