Ammianus Marcellinus Res Gestae 15.10.2

[2] Now on the southern side it is washed by the Tuscan and the Gallic Sea; where it looks up to the heavenly Wain, ¹ it is separated from the wild nations by the channels ² of the Rhine. Where it lies under the west-sloping sun ³ it is bounded by the Ocean and the Pyrenaean heights; and where it rises towards the East it gives place to the bulk of the Cottian Alps. There King Cottius, after the subjugation of Gaul, lay hidden alone in their defiles, trusting to the pathless ruggedness of the region; finally, when his disaffection was allayed, and he was admitted to the emperor Octavian’s friendship, in lieu of a remarkable gift he built with great labour short cuts convenient to travellers, since they were midway between other ancient Alpine passes, about which I shall later tell what I have learned.