The most famous part of the circuit is the Eau Rouge and Raidillon combination. Having negotiated the La Source hairpin, drivers race down a straight to the point where the track crosses the Eau Rouge stream for the first time, before being launched steeply uphill into a sweeping left-right-left series of corners with a blind summit. Properly speaking, the Eau Rouge corner is only the left-hander at the bottom. The following right-hander that leads steeply uphill, which was introduced in 1939 to shortcut the original Ancienne Douane hairpin, is called . The corner requires an amount of skill from the driver to negotiate it well and the long Kemmel straight ahead produces good overtaking opportunities for drivers at the following "Les Combes" corner. The corner was tighter and narrower before 1970, allowing drivers to take the corner faster.