The round around the Hennesee offers 15 flat (for Sauerland conditions; o) km with almost continuous view of the lake. Unfortunately, the southern part of the west bank leads across the bike path parallel to the B55, but you can live with that. But the other 3/4 are very quiet and idyllic.
The east bank offers with marker stones at 100 m distance good opportunities for interval work. The local athletes like to use the lap for marathon preparation (2 laps = 30 km as a long run). Another highlight is the Himmelstreppe on the northern flank of the dam. With 55 meters of altitude on 333 steps, you have a "training device" that does not exist too often.