Fascinating city. We stayed in the heart of the city a Clarion Twenty-seven (watch out for the Ice Bar, they party late and the music is loud). We walked most everywhere and there are jump on/off buses to get you to some of the further tourist spots. Additionally, you definitely want to take the canal tour. It will give you a whole different perspective on the city. Prices are expensive. The Clarion had a breakfast and dinner buffet included in the room price which made it an extremely good value. However, the room was very small and utilitarian.
Fascinating City but oh, the traffic. Expect to spend time in traffic jams. We visited Yusupov's palace where Rasputin was assassinated and Catherine palace in the country. The decadence of that era is astounding. The Church of the Spilled Blood and St. Peter's Cathedral were beautiful.
Did a land/sea tour in Stockholm. Beautiful city melding old and new together as only the Swedes can do. The Vassa museum is really interesting if you like old ships. Our sea tour was tour hours long including a trip through two locks, very cool.