about 15 000 years ago. The end moraines of different glacial retreats have been conserved. Glacial landscapes A look at a map still reveals the directions where the ice age glaciers ran. The farthest expansion of the Rhône Glacier to the northeast is indicated by way the western Swiss Plateau valleys trend: The valleys of the Broye and the Glâne as well as Lake Murten, Lake Neuchâtel, and Lake Biel that trend all northeast, parallel to the Jura and to the Alps. The glaciers of the Reuss and the Limmat have carved the valleys of the central Swiss Plateau that trend northwest (among others including the valleys of the Wigger, the Suhre, the Seetal, the Reuss and the Limmat). The Rhine Glacier has mostly left traces that trend west: The eastern Swiss Plateau of the Thur Valley and Lake Constance. In certain places, there are characteristic drumlins of the base moraine, often clustered, especially in the highlands of Zurich, in the Hirzel region, in the Lake Constance region and between the Reuss Valley and the Lake Baldegg. Another reminder of the glaciation are glacial erratics which are found all over the Swiss Plateau. These rocks, sometimes of enormous size, are of alien stones, mostly granite and gneiss from the central crystalline Alps. Taken together, they were one of the clues that led to the substantiation of the glaciation theory in the 19th century since transport by water or by volcanism was physically impossible. Gravel deposits in the bottoms of the valleys are another testimonial of the glaciation. During the advances and withdrawals of the glaciers, gravel layers were deposited in the valleys, sometimes quite thick, though most of it eroded in the subsequent interglacials. Therefore, many valleys have characteristic terraces, the lower terraces consisting of Würm glaciation gravel, the higher terraces of Riss glaciation terraces. Sometimes, there is also gravel from older glaciations. Topography Even though the Swiss Plateau forms a basin, it is by no means a flat territory, but depending on the region, it has a manifold structure. Important elements are the two big lakes, Lake Geneva and Lake Constance that delimit the Swiss Plateau in the southwest and the northeast. The western plateau is stamped by the Gros-de-Vaud plateau (up to 600 meters AMSL) and the Jorat molasse hills (up to 900 meters AMSL) but is sometimes intersected by deep valleys. Only near the Jura, there is