Plus d'infos et topo :
http://cinqplus.blogspot.com/2012/06/topo-tabir-sarrail.html
Parking on N942 Chaussรฉe de Gramptinne (village Faulx-Les Tombes) 50.42812, 5.00081. Walk down the road, passing the castle, take first path on the right and cross the bridge over the river Le Samson. Follow the main trail, after about 100m you'll already see this nice wall on your left.