St. Petersburg (Russia) in July-Aug.

I'm giving a talk at a meeting in St. Petersburg in July--my wife is coming along as well and we are staying a week after to do some sightseeing. On the agenda are the Winter Palace, Hermitage, River Neva cruise, Dostoyevsky sites, and the University (I have a colleague who is a professor there). I am very interested in all the architecture, inside and out, and possibly a side trip to Moscow and/or Helsinki. Can anyone recommend anything else that would make interesting subjects, or any particularly interesting vantage points? We should have around 20 hours of light / day at that time of year!

Thanks,
Kevin

PS: any restaurant recommendations would be appreciated as well.