I heard the Russians had him cremated, so if not so scientists could clone his brain?
What a lot of people don't know is that the Germans saved a bit of his tissue long before burning his body.
This tissue was smuggled out of Germany to a base built in Antarctica. The Germans built the base as soon as the war was looking bad,
with the help of the civilisation that lives there.
Aside from that, I know they worked on all sorts of experiments there--much of it bio-mechanical in nature.
There was also research being conducted on super-soldiers,
that would re-emerge from the Earth when the time is right. The Russians didn't know about it.