If You Have 1 Day -- Arm yourself with a bag of freshly cooked shrimp -- purchased right off the shrimp boats at the harbor in front of the Rådhus (Town Hall) -- and take a ferry over to the Bygdøy Peninsula. Visit some of Oslo's major attractions -- they're within walking distance of each other. Explore the Viking ships, the polar ship Fram, the Kon-Tiki Museum, the Norwegian Maritime Museum, and the Norwegian Folk Museum. In the late afternoon, go to Frognerpark to admire the Vigeland sculptures.
If You Have 2 Days -- On your first day, follow the itinerary above. On your second day, take the Frommer's walking tour and have lunch in a Norwegian restaurant. In the afternoon, explore the Edvard Munch Museum. In summer, during clement weather, visit Studenter Lunden, the students' grove near the National Theater, for some beer and fresh air.
If You Have 3 Days -- For your first 2 days, follow the itinerary "If You Have 2 Days". On the morning of Day 3, take another Frommer's walking tour, eating lunch along the way. In the afternoon, explore Akershus Castle and the adjoining Norwegian Resistance Museum. By late afternoon, visit the lofty lookout tower at Tryvannstårnet and see the Skimuseet at Holmenkollen, taking in the sweeping view of the Oslo environs. Have dinner at Holmenkollen.
If You Have 5 Days -- For the first 3 days, follow the itinerary "If You Have 3 Days," above. On Day 4, head south from Oslo for a 1-day excursion to the Oslofjord country, with stopovers at the Old Town at Fredrikstad; Tønsberg, Norway's oldest town; and Sandefjørd, an old whaling town. Head back to Oslo for the night. On Day 5, see the rest of Oslo's major sights, such as the National Gallery, the Historical Museum, and the Henie-Onstad Art Center, 7 miles from Oslo -- a major museum of modern art.