Before the Second Age, Belegaer stretched from the Gap of Ilmen in the far north, where a bridge made of ice known as the Helcaraxë connected Middle-earth and Aman, to the far south, where it also connected with Ilmen and froze.
The Ilmen Slavs seem to have been different from other Slavic tribes colonizing what is now Russia in that they were closely related to the Polabian Slavs in language and traditions (see old Novgorod dialect and Gostomysl for examples).
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The land of the Ilmen Slavs later became the center of the Novgorod Republic.
The basin of Lake Ilmen contains vast areas in Novgorod, Pskov, and Tver Oblasts of Russia, as well as minor areas in the north of Vitebsk Region in Belarus.
Олег Митяев и Владимир Кристовский ("Concert on Ilmen Fest. Oleg Mityaev and Vladimir Kristovsky)
After regrouping the army advanced north and south of Lake Ilmen on the Novgorod-Chudovo-Leningrad and Staraya Russa-Kholm-Demyansk axis.