ridge of high land, western Russia, running in a west-southwest to east-northeast direction across the Russian Plain from Orsha, southwest of Smolensk, to Yuryev-Polsky, northeast of Moscow, a distance of 420 miles (680 km). Marking the southern limit of the last glaciation, it consists of limestones in the east and glacial detritus, or disintegrated rocky material, in the west. Its maximum elevation is 1,050 feet (320 m). The route along the ridge is that which has been followed by many invaders of Russia, most notably by Napoleon in 1812.