The steep-sided Meuse River valley has long been an important tourist area. After rolling across northern France, the Meuse takes an L-shaped course through Belgium, and then crosses into Holland (where its name changes to the Maas). Along its Belgian banks are historic towns, strikingly situated châteaux and abbeys, impressive scenery -- and aging industrial plants and smokestacks that spoil views, particularly around Liège.
It's best to do the Meuse Valley as a driving tour, beginning at Liège and heading upstream to Namur, Huy, and Dinant. But it's possible to tour by train and bus, thanks to frequent and fast connections. In that case, you should base yourself in either Liège or Namur.
From Dinant, either head east into the Ardennes, or go west into Hainaut, the lush and verdant, lake-speckled "Green Province" that stretches along most of Belgium's border with France. Tournai and Mons are the repositories of great art and historical treasures.