Hello, if you want to do your own thing in St. Petersburg then yes you need Russian visas which cost £100 each and I understand take about 4 weeks to acquire. We did not have them so were forced (as is everybody on any cruise line without single visas)to go on the ship's organised excursions. On Crystal the excursions were from $57 up to $300 depending on what you did. Your cruise line will give you a list of their excursions I'm sure prior to leaving so you can read through what's on offer and decide. Can't help with doing your own thing locally but am sure they would be cheaper but it's a vast city and not the kind you can walk around like Paris. If you are going on Crystal then log on to their website with your booking ref etc and you can read all the tours on offer at any place for your cruise. The palaces outside the city like Peterhpf and Catherine are a minimum 1hour drive away from the port. Some tours were 8-9 hrs and although we didn't do one, other passengers said it was too much and far too long a day. 3 days isn't anything like enough so just do some homework first. Buy a book on the city from Amazon. Enjoy your holiday!