All kinds of fun routes:
http://www.rando-cretes.fr/circuit/134-la-fontaine-rouge
Mountain biking:
Near Mainbresson, there are numerous mountain bike trails available. Some of these routes can be easily reached by bike, while for others, it is recommended to drive to the starting point. Here is a summary of the different trails:
*From Mainbresson you can cycle to the forest between Brunehamel and Ribeauvillel. At about 7 km is this forest with some mountain bike trails
* In the valley, just before you cycle out of Mainbresson, you will see on the left and right the possibility of following a mountain bike trail. It is a beautiful route that winds around the little river Serre
*Somewhat further away is Aubenton with some fine trails. See the following link for more information:
http://www.randonner.fr/rando/veloroutes-et-voies-vertes/la-haye-d-aubenton/
In Hirson, there is a vast nature reserve offering various options for outdoor activities. You can enjoy mountain biking on the numerous routes available. If the "little office" is open, you can obtain a map to guide you. Otherwise, it's an adventure to explore the different routes on your own, which, from my personal experience, is perhaps the most enjoyable way to do it.
http://www.picardietourisme.com/nl/sejour-picardie/loisirs/thierache-sport-nature-004.aspx
Road bikes:
There are very interesting road bike routes.
Tip: stay off the RN (Route National) roads as much as possible and cycle by road. The variety of small charming villages and tough hills make it very pleasant to spend a few hours on the road bike.
In a number of villages there is a bar to have a cup of coffee or fill your water bottle. Be aware that between villages you will hardly find anything. It is advisable to have a good navigation at hand, e.g. Outdoor Active.