If you don't take the Sapsan to St. Petersburg, you can go the conventional train way. Kade and I did the overnight train, which took over eight hours. The clip below shows the train we took, except we went the opposite direction. After this video, scroll a tad to see some friends (and residents of Russia) who took their own journey to St. Petersburg from Moscow. Renata and Dilya had a wonderful time. All aboard!
For a bit of history about the railroad connecting St. Petersburg and Russia, click here.
UPDATE: Click here to see Anthony Bourdain on the midnight train to St. Petersburg.