It appears you have to take an excursion here, we went with SPB Tours and had a bus driver and a local guide for just ten people. There is just too much to write about the amazing buildings, churches and museum which we visited. We were the only visitors at both "off the beaten path" local restaurants where we had excellent lunches.
We just drove through the city which looked ok, we then went on a vintage train ride which was very expensive and definitely not worth the money. Our friends rented bicycles on the dock and quite enjoyed their visit.