In Liège, the whores can be found near the Rue Léopold, Rue de la Cathedrale and Rue L’Agneau.
Also you can find some windows at the station near Liege-Guillemins, on rue Varin.
Seraing (borough hatch) window prostitution in the Rue de la Glaciere
You can read more from: http://www.wikisexguide.com/wiki/Belgium