My apartment is close to everything. It is just a 10 minute walk (3 min by bus) to the central station and the main shopping street, Karl Johans gate. The neighborhood Grünerløkka is a very pulsating part of Oslo with a lot of cafes, restaurants, bars, and vintage shops. A short walk through the beautiful Botanical gardens will take you to the Munch museum. The apartment is facing the backyard, so although very central it is nice and quiet inside. You will also get access to a rooftop terrace.
As mentioned the apartment is very close to the central station where the airport express train stops. It is a 5-10 minute walk to the closest metro station, and 3 different buses and one tram stops right outside the door.