I had such a great time staying at Martin & Gung's. The location was incredibly convenient (just steps from Grønland station and about 10 mins walk to Oslo S) and very close to a grocery stores, tons of eating places and popular tourist sites. The travel card included was incredibly helpful too. The room was really spacious and it was very quiet at night. I was usually out the whole day, so i didn't get a chance to spend a lot of time with Martin or Gung, but when I arrived Martin had some really great suggestions of places to see, and at least one of them was always around if i needed anything. Also, since there are 2 other rooms they rent out, you get to meet other international travellers too! If you're looking for a place to stay in Oslo, i would definitely recommend staying with Martin and Gung!