If you want a more scenic alternative to the E16, you can take Austsidevegen. The name simply means "the east side road" – it runs along the eastern side of the river Begna, parallel to the main highway. You can exit onto it just north of Nes i Ådal by crossing the Haugsrud bridge, and it will bring you back to the E16 further north.
The main reason to take this detour is Piltingsrud farm. This is a traditional Norwegian farm that's been in the same family since 1796. The buildings all date from before 1850, and the whole complex sits idyllically by the river. They raise grass-fed Aberdeen Angus cattle without any grain feed, which is quite unusual for Norwegian meat production.
The farm has a shop that's open around the clock, year-round, selling their own beef, cured sausages, honey from their own bees, and local handicrafts. During summer, there's also a café in the courtyard. If you want to stay overnight, they have rooms in the restored farm buildings.
There's also a small cave nearby called Piltingsrudhula. It was actually carved out by the farm's former owner, Pedor Piltingsrud, who intended it to be his burial site. He was quite a character.