About the location
The Opera House, the Akershus Fortress and the Holmenkollen Ski Jump Arena are great spots for architecture photography. Oslo is at the top of Oslofjord, surrounded by forests and mountains. There are about 40 islands in and around the city. That's why the environment of Oslo has a lot to offer in terms of landscape photography as well.
Oslo is worth a visit during every season of the year. The gulf stream brings for scandinavian conditions a relatively mild climate to Oslo even in winter.