I have always been drawn to view points and although I cannot remember exactly how I ended up in this place, I must have been out looking for good views over the city. I go back here every now and then, when I feel I need to get an overview of the world (or at least my neighborhood). Seeing the city from above helps me put things into perspective.
This is not a marked or exact view point, so to find it you have to go to Gamle Aker Kirke, which is within walking distance of most central spots in Oslo. Once you get there, go on the trails in the graveyard until you get to the edge, look out, and voila; here is your view point. Walk around a bit to find your favourite spot, and see if you recognize any landmarks or buildings.
It is beautiful any time of day and in any weather, but I recommend visiting in the afternoon/evening light on a sunny summer day to see the Grünerløkka neighbourhood painted in pink below you. It takes a long time before it gets dark in Oslo in the summer, so no need to worry about getting stuck in the graveyard in the dark.