Frozen lakes, pine trees, hills covered in snow, frozen sea, tall people, calmness.  

A few tips if you are planning a visit:
For vintage, independent shops and cafes walk around Grünerløkka. My top choices are Mitt lille hjem for little gifts, Parkteatret for live music or just a drink, and Barrio for burritos and mexican cocktails. 
For street art, art galleries, walk on Brenneriveien street. 
Visit the National Opera, walk to the top but also have a look inside.
Make sure you check the Film Museum and why not catch a film at Cinemateket.
Walk along Akershus Festning and if the weather allows it take a boat trip to the Oslo Fjords. 
Peak through any open doors on the street to check the yards of the buildings. 
Visit the Future Library
If you are interested in doing some swing dancing Winter Jump is a great festival. All year round check Bardar Swing Club