range of hills in W European Russia, between St. Petersburg & Moscow, forming a watershed for rivers flowing to the Baltic & those flowing south & southeast, esp. the Volga
See Valdai Hills in American Heritage Dictionary 4
also Val·day Hills(väl-dīˈ)
An upland region of northwest Russia between St. Petersburg and Moscow. It forms the watershed for numerous rivers, including the Volga, the Western Dvina, and the Dnieper.