This fortress is situated in the Vologda region, more than 400 kms from St.Petersburg. You may take the train to Vologda, then the bus to Kirillov city (there are 5 buses per day from 6.00 till 18.00, distance - 130 kms, 2 hrs). There are two buses from Cherepovets also.
There is only one hotel in Kirillov city and not a bad turbasa (tourist's camping). The hotel named "Rus" (phone - 3-15-39). Turbasa phone is 3-16-31. One bed room in hotel costs 250 rubles (near to 8 euro). The hotel is very good. You can easy get a boiling water for the free. There is a sauna (banja) for additional fee. It is strictly recommended to reserve the your rooms in advance.