I’m going to Oslo at the end of March. I’ve got a free day and fancy doing something different from the usual sightseeing. Has anyone been mountain biking near Oslo? Particularly the sommerpark as it looks easy to reach from the city centre. If not sommerpark, then where else is good to go riding for a day? I’ll need to hire a bike.

I’m not sure about biking but I went for a walk at Sognsvann for an afternoon and it was awesome. It was great to be able to get a direct train there from the city centre. I hope you can figure it out!

I think you will out of luck with the sommerpark it will be closed in the winter
It depends what you like there are many museums in Oslo
The Fram is good http://www.frammuseum.no/Home.aspx take the boat across Oslo fjord
http://www.vigeland.museum.no/en/vigeland-park
or just outside Oslo at Holmenkollen there is theSki museum where you can look down the ski jump and a great view across Oslo and the fjord with the Biathlon Stadium nearby that is where I will be in the middle of March to watch the Biathlon take the T-Ban to get there
travel around Oslo is ease you can get a ticket which gives you unlimited travel on the bus, tram T-ban and ferry if you stay in inside the zone A
Tavel from the airport don’t take the express train just use the NSB its half the price of the express train. They both go to Oslo central station but the express is every 20 mins and only goes to the airport and Oslo central station and Back the NSB is every 40 minutes and stops on the way I think its 3 stops to Oslo the ticket station is just outside the airport door and the staff speak english and really helpful
never done any biking I go to watch the Biathlon every year but found this maybe of help https://www.wikiloc.com/trails/mountain-biking/norway/oslo
Enjoy your stay we do

Regards Gary