Nestled in the Ardenne hills, it is unanimously considered the most complete track in the World Championship for its combination of fast turns, blind corners, elevation changes and infinite straightaways. This is the 51st time Formula 1 has returned to the track, but the circuit has changed dramatically over the course of the years: since 2007 is has measured 4,352 miles, making this the longest track in the World Championship. It stands out for having 19 turns, yet it only has four braking sections characterized by extreme outputs of energy. The cooling off of the braking systems is guaranteed by the presence of big, fast corners like Eau Rouge and Blanchimont, where the brakes aren't touched at all. The unknown variable is the weather: Last year, the air temperature reached 75,2°F but in 2014 it didn't go over 60°. According to Brembo technicians, who have classified the 21 tracks in the World Championship, the Circuit de Spa-Francorchamps is one of the least demanding on the brakes.