Sizov worked closely with both Uvarovs in several fields. First, he with Alexei he dug in kurgans all around the empire, and he helped them to establish the Historical Museum. His most important finds were in the Gnezdovo kurgans in the NW, around Smolensk, where he found evidence of Slavs and Varangians living peacably together; from this he postulated that the Varangians were the aristocracy in the region. Later he participated with Praskovia on her Materials of the Archeology of the Caucasus. He served on the Commission for the Preservation of Ancient Monuments, but also found time to work with the Imperial theatres.