Tacitus, Germania. Chapter 1.
1. Germany is separated from the Galli, the Rhaeti, and Pannonii, by the rivers Rhine and Danube; mountain ranges, or the fear which each feels for the other, divide it from the Sarmatae and Daci. Elsewhere ocean girds it, embracing broad peninsulas and islands of unexplored extent, where certain tribes and kingdoms are newly known to us, revealed by war. The Rhine springs from a precipitous and inaccessible height of the Rhaetian Alps, bends slightly westward, and mingles with the Northern Ocean. The Danube pours down from the gradual and gently rising slope of Mount Abnoba, and visits many nations, to force its way at last through six channels into the Pontus; a seventh mouth is lost in marshes.
Tacitus, Germania - translated by Alfred Lord Church and William Jackson Brodribb.