Oslo. You could sprint through Oslo sights and attractions in two full days (three nights), or enjoy Oslo strolling about in three full days (four nights). My arrival day is usually spent getting oriented and walking about.
Two day sprint plan. The Oslo 48 hour Pass may be worth the price and save time buying transit and entrance tickets:
https://www.visitoslo.com/en/activities-and-attractions/oslo-pass/prices/
You can cover the Bygdoy Peninsula museums and attractions in a day and visiting Oslo City Hall after the boat ride back from Bygdoy: https://www.visitoslo.com/bygdoy
Ferry from the Fram Museum goes to the pier near City Hall, the Nobel Peace Center and AkerBrygge complex. If you are staying in the central Oslo area, walk back from City Hall via the Akershus Fortress and views of the fjord from the fortress ramparts.
Second (or first) day. A lot to see in Oslo including Vigeland Park, National Museum, the Scream, Resistance Museum, taking the Metro T1 to Holmenkollen and the ski jump museum and tower. You can sprint or stroll Vigeland Park and its sculptures. Walk the Opera House roof.
https://www.ricksteves.com/europe/norway/oslo
At a Glance ▲▲▲ City Hall Oslo's artsy 20th-century government
building, lined with huge, vibrant, municipal-themed murals, best
visited with included tour.
▲▲▲ National Gallery Norway's cultural and natural essence, captured
on canvas.
▲▲▲ Frogner Park Sprawling park with works by Norway's greatest
sculptor, Gustav Vigeland, and the studio where he created them (now a
museum).
▲▲▲ Fram Museum Captivating exhibit on two Arctic exploration ships.
▲▲ Norwegian Folk Museum Norway condensed into 150 historic buildings
in a large open-air museum.
▲▲ Norwegian Resistance Museum Gripping look at Norway's tumultuous
WWII experience.
▲▲ Viking Ship Museum Impressive trio of ninth-century Viking ships,
with exhibits on the people who built them.
▲▲ Kon-Tiki Museum Adventures of primitive Kon-Tiki and Ra II ships
built by Thor Heyerdahl.
▲ Oslo Opera House Stunning performance center that's helping
revitalize the harborfront.
▲ Akershus Fortress Complex and Tours Historic military base and
fortified old center, with guided tours, a ho-hum castle interior, and
the excellent Norwegian Resistance Museum (listed above).
▲ Norwegian Maritime Museum Briny voyage through Norway's rich
seafaring heritage.
▲ Ekeberg Sculpture Park Hilly, hikeable 63-acre forest park with
striking contemporary art and city views.
▲ Edvard Munch Museum Works of Norway's famous Expressionistic
painter.
▲ Grünerløkka Oslo's trendy former working-class district, with
bustling cafés and pubs.
▲ Aker Brygge and Tjuvholmen Oslo's harborfront promenade, and nearby
trendy neighborhood with Astrup Fearnley Museum, upscale galleries,
shops, and cafés.
▲ Holmenkollen Ski Jump and Ski Museum Dizzying vista and a schuss
through skiing history, with a zip line off the top.
Norwegian Holocaust Center High-tech look at the rise of
anti-Semitism, the Holocaust in Norway, and racism today.
Nobel Peace Center Exhibit celebrating the ideals of the Nobel Peace
Prize and the lives of those who have won it.
