Biking around the lake Thun was more difficult than expected for two reasons: the sunny and warm day invited everyone to walk on the docks (which is pleasant outing), and we had to bike on the main road quite a lot. But still, we managed to appreciate the deeply blue color of the lake and the imposing mountain background. I can see why it is very popular! You can spend a full day visiting Thun old town and Spiez which are two very attractive places.
https://goo.gl/maps/qL1arcuiejF7aRUeA
https://www.myswitzerland.com/en-ch/destinations/lake-thun/