I think this is one of my favorite relaxing places in the summer, in Oslo. It is part of the few islands that can be seen and visited from Oslo center, if you take one of the boats at Vippetangen. But unlike the other islands, it is not common to visit for tourists and it is mainly for private summer houses.
Hence, there is no shop and only a few available public toilets so it’s best to just bring along anything you need. The beaches are not extremely friendly as surface and for entering the water I really have to watch my step. But it’s much more calm and quiet than on any other island.
But the views either over the city or the fjord are just breath taking. I saw incredible sunsets there, I enjoyed listening to the waves in the pseudo dark Norwegian summer evenings and I also got to fish for some baby crabs.
So you can’t plan a stay overnight there or you won’t find places meant for tourists, but on your way to the other islands, a stop here could be nice. The boat always stops here before going further so one can just catch the next one. And don’t forget to collect your trash and throw it away in one of the trash cans that are constantly emptied. The website where you can read about the island is in Norwegian but a translator might help you get more info.