I also really like Marbach and Luhmuhlen! I ride most of my international ckmpetitions in germany and at “turnier nennungen” you can find the calender. I dont know where you live but for me Strzegom and Sopot (Poland) are also super nice! They are almost as far as for example Marbach and Kreuth.
Munster, Kreuth Ostbevern!