Be sure to check out the medieval Old Town, Gamla Stan, known for its maze of narrow alleyways; the ceremonial changing of the guards at the 600-room Royal Palace (no longer the royal family's residence); Drottningholm Palace and Theatre, located on an island on Lake Mälaren; and the Vasamuseet, a museum inside the royal warship Vasa, which in 1628 sank to the bottom of Stockholm's harbor as it was about to begin its first voyage. Or you can take advantage of optional guided sightseeing tours, which start from €32 for an adult and from €22 for a child for a two-hour tour of the waterways of Stockholm.

In the afternoon, you'll board your ship to commence the overnight sail from Stockholm back to Copenhagen, from where you'll fly back to the U.S. If time allows, visit some of the city's major treasures, such as the Amalienborg Palace, home to the Danish royal family since the 18th century; the statue of the Little Mermaid, erected in honor of author Hans Christian Andersen; and the 150-year-old Tivoli Gardens amusement park. If you still have time to spare, you can join an optional 2.5-hour tour of the city for €47 for an adult and €33 for a child.

Nyhavn Canal in Copenhagen, Denmark (MedioImages/Corbis) [enlarge photo]

Not ready to leave? Additional nights start from $139 per person at Copenhagen Admiral Hotel. Before you go, visit the official tourism websites for Denmark, Estonia, Russia, Finland, and Sweden.

Getting There A recent search on Kayak showed that the lowest round-trip fares to Copenhagen, for travel during the first two weeks in September, start from $681 from New York (Icelandair), $953 from Houston (Continental), $996 from Chicago (multiple carriers), and $1,051 from L.A. (Continental).

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