In the Middle Pleistocene, Eurasia was affected by three major glaciations. The extent of the oldest glaciation, the Don glaciation, is still incompletely known. Also, for the Elsterian glaciation, the eastern limits are only roughly estimated. The ice sheet may have covered the west Siberian lowlands. However, it may have been the most extensive glaciation in eastern central Siberia. In the Saalian, the Older Saalian glaciation was the largest. It may have been the most extensive ice sheet in western Siberia, but the limits are still unclear, and west of the Urals the Saalian limit is not very well-defined. Middle and Younger Saalian glaciations were much less extensive. Correlation of the Nordic glaciations with the glacial sequence of the Alps is still difficult, and it seems clear that more glaciations occurred than Penck and Brückner had originally envisioned.