Battle of Waterloo (start/end: the Lion)

Passing by the Ferme de Hougoumont (a 9 hours batle-within-the-Battle, which he Allies held, and which Wellington claims to be the main reason the Allies won), Napoleon's obsevatory as from 4:00 pm, Napoleon's HQ, the village of Plancenoit (afternoon battle between the Prussians, coming from the east, and the French Young Guard, eventually enabling the Prussians to attrack more French troops and ultimately stop the advance of the French Old Guard, around 8:00 pm), the Ferme de la Papelotte (Prussian HQ when they arrived around 7:00 pm), Wellington's observatory (the whole day), the Ferme de la Haie Sainte (which Napoleon managed to conquer and equip with artillery around 7:00 pm, nearly winning the Battle for him), Wellington's HQ at Waterloo (the battlefield itself is actually in Braine-l'Alleud, but Wellington liked to name battles after the place of his HQ), and back to the Lion via the famous hollow road (which is no longer hollow because it was leveled since then, notably to build the mound for the Lion - probably the biggest historical/touristic mistake of all, closely followed by the chopping of the tree at Wellington's observatory to sell chops of it on the London market). 

Half of the route is to Wellington's HQ in Waterloo. The museum is interesting but the cycling route is not really that much fun, so you could also take other means of transportation to get there. Without cycling to Wellington's HQ, the route is 20 km (see my other Waterloo Battlefield route).