Joy's place is a beautiful, spacious basement flat below her house in Grefsen. It's a great location if you want to see some of the Norwegian countryside as well as the city.
To the city: a bus goes past the house every 30 mins but we tended to just get the tram at Kjelsas station. Loads of trams and it'll get you into the city centre in 20 mins or so. It's about 15 mins walk from the flat (it does involve climbing a big staircase past a pretty little waterfall).
The countryside: great access to nearby trails. There's also a great walk from Kjelsas into Oslo along the river.
The flat: basement flat but lit really nicely. The sauna, corner bath and open fire were great for helping us relax after a long day. If you want to eat out you'll have to go into Oslo, but there's a nice, big, well stocked kitchen with everything you need if you fancy buying some food and cooking.
The hosts: friendly, helpful and always quick to respond. Highly recommended.