F1 EXPLAINED: Things to know about the famous Spa-Francorchamps circuit

Before the final action kicks off at this weekend's Belgian Grand Prix, F1Technical's senior writer Balazs Szabo delivers some key stats and trivia related to the Spa-Francorchamps circuit.

The Spa-Francorchamps race track was designed by the chevalier Jules de Thier in 1920, who wanted to revive the La Meuse Cup, a car race that had been held before the First World War. The site for the circuit was marked out by a triangle formed by Routes 32, 23 and 440, connecting Spa-Francorchamps with Malmedy and Stavelot.

The first race was cancelled because there was only one entrant. The following event, which became the first race ever held on the 15.820km circuit, attracted 23 motorcycles.

In 1922, the Royal Automobile Club of Belgium organized the first car race on the circuit, an endurance event. The first Belgian Grand Prix was held in 1925 and was won by Alfa Romeo's Alberto Ascari.

Three years later, the track was paved to prevent stones from being thrown up by the cars. In 1939, the circuit underwent a major change. The old Customs Bend was removed and replaced by the high-speed corner known as Raidillon.

This resulted in the creation of the iconic Eau Rouge–Raidillon complex, linked by a steep uphill section with a 17 per cent gradient. It played a major role in establishing the circuit's international fame and reputation.

In 1951, the circuit was extended and the Stavelot corner was created. In 1963, the first safety barriers were installed around the high-speed track. In 1979, a much shorter 6.9km layout was introduced. The last major redevelopment took place in 2007. The famous, but problematic, Bus Stop chicane was rebuilt, while run-off areas at several high-speed corners were significantly expanded.

The 7.004km circuit features 19 corners. Following a relatively short start-finish straight, drivers brake down to just 90kph for the opening corner, La Source. Strong acceleration is vital because the following section is the longest period spent at full throttle not only at Spa, but anywhere on the Formula 1 calendar.

Turns 2, 3 and 4, the famous Eau Rouge–Raidillon complex, are taken flat out in a modern Formula 1 car. However, they remain one of the greatest challenges on the calendar, particularly in race conditions with degrading tyres or on a damp track.

The Kemmel Straight continues this flat-out section, with drivers spending around 18 seconds at full throttle. The end of the straight provides the best overtaking opportunity on the circuit and, with DRS, passing can be relatively straightforward if a driver stays close enough to the car ahead through La Source and Eau Rouge.

The second sector begins with Les Combes. Together with Turns 7 and 8, it forms a fantastic sequence of corners where drivers require impeccable car balance: a strong front end through Turns 6 and 8, combined with a very stable rear through Turn 7.

The circuit then descends towards Turn 9, Rivage. This 180-degree corner demands patience on entry before drivers can focus on achieving a strong exit. Turn 10 encourages them to use every last centimetre of the wide kerbs to maximise exit speed heading into the next sequence of corners.

Turn 11, Pouhon, is taken at full throttle for almost its entire length. Turn 12, Fagnes, begins a sequence of three medium-speed corners where excellent car balance and high levels of downforce are essential.

Sector 3 starts with Turn 15, Stavelot. Exiting this medium-speed corner, drivers are eager to get back on full throttle, remaining flat through Turns 16, 17 and 18 before arriving at the Bus Stop chicane, which consists of two slow-speed corners.

As they exit the final corner, drivers are always on the limit of rear grip but still strive to apply full throttle as early as possible to complete the final metres of the longest circuit on the current Formula 1 calendar.