I am doing a riverboat cruise from St. Petersburg to Moscow and have enough points to book business or first through Air Canada, American, Delta or US Airways. That gives me access to a lot of airlines. We want to do one stopover either going there or home. We think we prefer to do it on the way over while still fresh rather than after 13 days on a riverboat. Any suggestions where to go. We are not interested in London, Paris or Rome. Our thoughts are Prague, Budapest, Copenhagen, Munich or Berlin. We would spend four nights there. That gives us 3 1/2 days to tour before we head to St. Petersburg or home.