A bundle of four road books in the Thiérache region (North of Laon) will allow you to discover of four valleys dotted with fortress like churches. This one leads you along the Thon river. MORE ABOUT...
This road book wil not bring you to the feet of each monument, but will simply refer to it in the waypoint at the screen when entering the pertaining village. To you to discover it.
Do not miss either, more South, the nice ride along the Chemin-des-Dames (RB #932) and the road books of the other valleys: Oise, Serre and Brune