Starting in Achouffe, you can do a beautiful 8km hike. It is a round trip that can be extended to around 12k.
In the beginning, you have to cross a little river but because it is not deep, this is fairly easy to do: take off your shoes and socks, roll up your pants and just go.
You follow the river constantly while walking in between the trees. At the end, there are some ups and downs but the most part is flat.
Here are some pictures we took along the way.