Hitler will have it burned to the ground and it's people will be murdered en-masse.
Don't be ridiculous. Too visible. Read somewhere the siege of the city was in order to make veryone starve, but perhaps that was just an excuse for having the German army attack an area where a million people would fight to the death. Actually, I wonder if Hitler wouldn't just have a lot of people moved around, having the city turned into winter quarters for the army. Plenty of housing there. I imagine a lot of quarantines to limit people to overcrowded areas to starve, freeze, etc would work. Just need to turn off utilities. Innretrospect, maybe they would actually destroy all the historical buildings, despite my saying they wouldn't if they got there fast. The Baroque architecture was pretty French inspired. Still, places like the Hermitage had plenty of German art (it started ffrom stuff Catherine the Great bought form a Berlin art dealer) so I can see a lot of the interior of palaces, at least those that hadn't been thoroughly looted by Bolsheviks, revolutionaries, and looters, to be stripped down or dismantled, being used for museums across Germany.
What I think would be fun is some massive set of revolts or mutinies in order to bring the greater Ingria area free of the Soviets. Mainly as it would lead to some annoyance by the Axis and others on whatever to do with it, as invading it would make the Germans look like they weren't doing all of this as a crusade to save everyone from communists. Still, not a great loss for Russia if there was a state set up that same to claim or take the old territory of the Novgorod Republic. Mostly places in the north anyways. Part of the same reason why Hitler was fine with all of Karelia going to Finland, and why Himmler was intent upon pressuring Finland into taking land in northern Sweden and Norway (The Finns declined, even when offered to just have it handed to them). The land was pretty cold and wouldn't be of much use to themselves.