Topcamp Onsakervika is located by the Tyrifjord and is known for having Eastern Norway's perhaps finest sand beach. You may be thinking of this as a summer destination, but there is plenty to do in the area in early fall as well!
Fall at Topcamp Onsakervika
The most spectacular experiences in the area around Topcamp Onsakervika are the hikes Mørkgonga and Kongens Utsikt. Mørkgonga can be a bit difficult, but the view from the top is quite spectacular. It will be especially spectacular if you go up by sunset and see how the already orange leaves are colored even more golden. Kongens utsikt is a 2-3 hour walk up from Sundvolden Hotel, but you can also drive up to Kleivstua and walk around 30 minutes from there. If you want an even shorter trip, Dronningens utsikt is a good alternative, the view is great here too.
Close by is the Kistefos Museum, which is more than just a museum. Here they have the world-famous "The Twist", sculpture park, play equipment and more. Hadeland Glassverk is close by as well. Which is kind of a shopping center where you can do everything from shopping, blowing glass or going to the children's farm.
The bakery and pizzeria at Hadeland Glassverk are worth a visit, with delicious stone oven-baked Italian pizza. There are many nice places to eat in the center of Hønefoss. Brasserie Prison serves a classic à la carte menu. You get really good local food at Thorbjørnrud Hotel by the Randsfjord. You can also get really local food if you visit Ringvold Eplehage, which is Norway's largest apple orchard. They offer self-picking of plums in August and apples in September.
It is also quite possible to swim in the Tyrifjord in August and September - at least if you are a happy swimmer. If you like the water, but not the degrees, you can take the SUP-board out, or a kayak or canoe. Topcamp Onsakervika rents out SUP boards, pedal boats, and canoes. Or you can go to Ringeriksbadet, which has several pools, water slides, a sauna, and dining.