Belgium
You will find easy cycling paths along previous railroads (Ravel), canals and rivers, while parts of East Belgium are quite hilly. The scenery and variations in the landscape are beautiful and exciting.
The price level is relatively low. Accomodations and restaurants are easy to find; to reserve a table may be an advantage. Good cycling maps can be found on Internet, at tourist offices or in book stores. In many regions you will find road crossings marked with a number, telling you where you are on the corresponding map.
Some of the trips under Netherlands and Longer Routes go into Belgium.
Cycling route suggested:
The route is defined both with an electronical map (Strava) and as a series of fietsknooppunten. In winter there may be ice on the cycling paths.
Round trip 1 from Brussels (map link)
Brüssel – Charleroi – Namur – Liege – Hasselt – Grobbendonk – Brüssel