Subsequently, after hours of pounding across the Flanders flatlands and the occasional excursion to Northern France, the riders approach the hill zone in Heuvelland, which features the day's most difficult ascents. The hills are at the heart of the action and usually the sites where breakaways are formed. The race's most renowned climb is the Kemmelberg, a fully cobbled hill road in Kemmel with gradients up to 23%, but equally notorious for its difficult and technical descent.