I highly recommend vosges in France. For me from Germany (Frankfurt) it is really easy to reach in 3 hours. The area is very beautiful and perfect for biking, hiking and other sports. A nice place for an Airbnb is Gerardmer. Small cute little town with some basic cafes and stuff. There is also a lake (perfect for triathletes) and another lake nearby with a campsite. Recommended hills to ride: Col de la Schlucht, Plateau des belles filles, Grand Ballon, Markstein, Petit Ballon, Ballon d Alsace, Col du Page, Route des Cretes (Flat route of around 80km over some mountain tops), Col du Haag, col des chevrères. Whats really nice in vosges is that you have plenty of routes and most hills plenty of sides you could climb to the top so it is easy to ride routes in all different directions and you do not need to ride some roads twice or back and forth. Any places you guys recommend?