St. Petersburg is unique Russian city in many regards, and its clearly European architecture is one of its distinctions. You can even sometimes here people say that St. Petersburg is not a Russian city. Those who say so mean, no doubt, first of all its architecture, and secondly, its history of a city founded by Peter the Great as a “window on the West.”
However, there are quite a few ancient Russian cities, founded in the 9th - 12th centuries, where you can easily go to for one or few days by your choice. Of course, the first to mention are Pskov and Veliky Novgorod, located about two hundred kilometers away from St. Petersburg. Quite different in their architecture, they both have similar features of a medieval Russian city: centered around a Kremlin (the old Russian word for fortress), they are located on major rivers (then main transportation routes), had lived through many invasions of neighboring kingdoms, badly destroyed during World War II, fully reconstructed and now welcoming tourists with the many attractions they have.