In the Scandinavian Summer, the residents of Copenhagen and Stockholm come out to play. Their beautiful cities come alive: waterways glint in the morning sun, colors glow in the evening light and in between, all sorts of doors open up. There are museums, palaces and designer stores aplenty and friendly terraces where you can sample unusual dishes. Three days in St Petersburg will also prove irresistible to lovers of art, architecture and history. You'll marvel at treasures that rival any Renaissance city to the south. Tallinn and Berlin, too, show how recent changes to the political map have breathed new life into capitals determined to celebrate past, present and future.