Also, if you check out Rick Steve's books they have a walking tour for each city. inn Stolkcholm we did the hoho bus but in Tallin we used his tour and it was right on. Very exact in the way it describes things like "turn right at the very twisted tree by the church". You're thinking 'huh, what?' but then you get to this very twisted tree and know exactly what he's talking about.
Copy the pertinent pages and leave the book at home or on the ship. makes for a lighter pack when touring.