Geography has imposed significant constraints upon human activity in Graubünden throughout its history. The Rhaetian Freestate's sovereign heartland consisted of two major river valleys flowing out of the jumbled center of Europe. To the north is the Rhine: from its source at the Oberalpsee, it flows east along a nearly impassable line of mountains that separate Graubünden from the rest of Switzerland. All of the Rhine's major tributaries during its eastward course flow out of a series of deep-cut valleys from the south; the larger ones, especially the Domleschg, provide access to the passes that connect Rhaetia to northern Italy, most notably the Splügen (2117 meters) and the Septimer (2311 meters). The Rhine itself, having lost nearly 1500 meters of altitude, reaches the end of the confining northern range at Chur (585 meters), and turns north to flow towards the Lake of Constance. The lower reaches of the Rhine in Graubünden are one of the few relatively flat and fertile parts of the region: from Ems above Chur down to Fläsch, the valley broadens out into a “U” shape with gently rising fields on the eastern side of the river. Not only grain and pasture but also vineyards are found here.

Fifty kilometers to the southeast, parallel to the Rhine, the Inn begins its course down to the Danube.