Tøyen parkrun is cancelled on Saturday 25 May, as there is a festival on in the park. Festningen, Løvstien and, Stavanger are all on, and there are internal flights there. Dømmesmoen in Grimstad is also on, and is a 3 1/4 hour drive from here. A final option is Skatås in Sweden, which is a 3 hour drive from Oslo.
Another option if you’re in Oslo on Saturday is to take part in Ecotrail, with distances ranging from 10-80 km, through the forests and along the fjord.