The identity of Valdai is boulders, often found here as a reminder of the glacier's disappearance.

“The Valdai Hills consist mainly of sediments rich in boulders,
under which limestones and shales of the mountain-lime formation are widespread.
macia, rich, especially in the southern part, with its characteristic fossils" (https://ru.wikisource.org/wiki/ESBE/Valdai_gory)

During the "Valdai glaciation" glaciers reached the modern Valdai
Daisky hill. Glaciers descended from the centers of glaciation - Fenno-
scandia, Novaya Zemlya, the Polar Urals, carrying fragments of the rocks developed there over vast territories.

During the melting of the ice cover in the area of glacial accumulation (north-west of the East European Plain), moraine plains with hilly-ridged, hilly-western moraine relief, drumlin relief were formed.