For my very first road trip in Belgium, I left Heverlee and followed the N253, which is a scenic road that crosses several villages and small towns in the countryside: Egenhoven, Neerijse, Loonbeck.
From Huldenberg to Overijse, there is a nice little lake along the right edge of the road. I kept driving to Maleizen, then La Hulpe, Hannonsart, Ohain, Ransbeche, and finally Waterloo, where I visited the battlefield.
The museum was an excellent opportunity to take a break. I learned about the French Revolution, the rise and fall of Napoleon, and watched a very good 3D movie about the battle of Waterloo. Outside, I climbed the stairs on the hill (40m) which led to the statue of a lion, erected here as a memorial and the symbol of the return of peace in the world with the end of the Napoleon era. From there, I could enjoy the panorama since the weather was pretty sunny, with only very few clouds.