The Copper Door is by far one of the best AirBnBs I've had the pleasure of staying in. It's a short walk to some great sites, like Frogner Park & Vigeland Sculpture Garden with a few great restaurants & cafes along the way. There's even a little market within walking distance. The metro is less than a block from the apartment with a few lines to central station, again it's a short distance (maybe a 15 minute ride).
The apartment is impeccable, cozy, & beautifully decorated, I LOVED having coffee & espresso at my fingertips in the adorable kitchenette.
Jannike was out of town during our visit, but her husband Alf & their children were very helpful & accessible, if needed.
I highly recommend the Copper Door for any length of stay in Oslo, I hope I'm lucky enough to make my way back!