Few circuits are more revered than the mighty Spa-Francorchamps. The track has been synonymous with Formula 1 for more than 60 years, and, with an average speed of 230km/h (143mph), it's breathtakingly fast.
At more than 7km, the undulating circuit is the longest on the 2015 calendar. However, the existing layout is only half the length of the original design, which featured in the inaugural world championship of 1950. The current track - opened in 1983 - retains much of the original high-speed challenge, as well as many of the iconic corners like La Source, Eau Rouge and Blanchimont.
More than 70 per cent of the lap is spent at full throttle, which places an emphasis on the power unit and on the car's aerodynamic efficiency. There is also the unique situation of the machinery having to cope with a 1.7g compression at the bottom of Eau Rouge, which can prove a test of reliability over the 44-lap race distance.
The weather forecast is notoriously unreliable in the Ardennes region of Belgium. Temperatures of around 20 degrees are expected, but it's harder to predict the chance and the location of the rain. If wet weather comes it can affect only one section of the track - often several miles from the pitlane - which creates considerable strategic challenges.
In the event of dry conditions, the drivers have Pirelli's Soft (Option) and Medium (Prime) tyres at their disposal. These are the same compounds that were used at last year's race, when two pitstops were the norm for most cars. Should a Safety Car appear early in the race, a one-stop strategy is also possible.
McLaren has an indelible link with Spa-Francorchamps because it was here, in 1968, that the team won its first world championship grand prix. The team now has a total of 14 wins on Belgian soil, the most recent victory coming in 2012.
It's all about the race
Start time: 14.00 (local)/12.00 (GMT)
Race distance: 44 laps (full world championship points awarded after 75% distance/33 laps)
2014 winner: Daniel Ricciardo
2014 pole position: Nico Rosberg 2m05.591s 200.766km/h (wet)
2014 fastest lap: Nico Rosberg 1m50.511s 228.162km/h
Safety Car likelihood: Chances of a Safety Car High. There's an 80 per cent chance that the Safety Car will appear in Sunday's race - that's largely due to accidents at Spa occurring at high-speed
Don't put the kettle on: The start, when new FIA rules mean there will be more input from the drivers; and laps 13 and 28. Last year's race was won with a two-stop strategy and, changeable weather aside, the same looks likely in 2015
Weather forecast: Changeable. Spa-Francorchamps is located in the Ardennes Mountains, which have a notoriously fickle microclimate.
It's all about the track
First race: 1950
Circuit length: 7.004km/4.352 miles
Run to Turn One: 265 metres
Longest straight: 2.015km, from La Source to Turn 5, Les Combes
Top speed: 322km/h on the approach to Turn 5
DRS zones: Two - on the approach to Turn 1 and, again, on the approach to Turn 5
Key corner: Turn 10, a 180-degree double-apex left-hander. The entry is fast (294km/h) and blind, and the drivers need to be totally committed in order to be fast
Pitlane length: 390 metres, which is quite long. The time loss isn't that great because the cars staying on-track have to negotiate the La Source Hairpin
Major changes for 2015: None
It's all about the car
Fuel consumption: 3.35kg per lap, which is high
Full throttle: 70%
Brake wear: Low. There are only nine braking events around the lap
Gear changes: 48 per lap/2112 per race
Fernando Alonso: "It feels great to be back. I enjoyed a relaxing break over the summer shutdown, but I also trained hard and I feel in the best shape to start the second half of the year. After Hungary, we were all really encouraged by the outcome; although we were fortunate to have had some good luck, we still battled hard and finished the race with a positive result.
"Spa will be tricky for us, due to the configuration of a track that requires power, downforce and a big chunk of the lap spent at full throttle. But, from a driver's perspective it's a spectacular circuit and the fans there also make it a truly special place. It's a place at which I won when I was in Formula 3000, but never in Formula 1. I've enjoyed some really exciting battles there, and I'm looking forward to this weekend for some more.
"The next few races will be important for us: we need to continue our forward momentum, and, with the addition of some tweaks to the car and power unit, we will be looking for more progress and good correlation between the simulator and our on-track performance. That might not necessarily appear above the surface in either Spa or Monza, but we'll keep pushing development forward at each race."
Jenson Button: "What a place to resume the second half of the season! It's such a great place to come to after the break - Spa is a circuit I've always loved right from the start of my racing career, and every lap around this incredibly special circuit is still hugely exciting and puts a massive grin on my face. It's genuinely a circuit like no other.
"I'm really looking forward to getting back into the car and seeing where we stand among our nearest competitors. We can't pretend that we're expecting a huge jump forward in performance - especially at this circuit, as it doesn't suit our car's characteristics - but, after the break, I'm feeling refreshed, positive, and ready to continue the solid progress we've made so far.
"I love Spa, I won there back in 2012, and, even when I'm not battling for the lead, I really enjoy the racing there as it usually produces fantastic grands prix. It's a privilege as a Formula 1 driver to be able to go to the circuit in the morning, get in the car, and race through some of the most legendary corners in motorsport."
Eric Boullier, Racing director: "After a well-deserved summer break for the whole team, we're all ready and raring to go at the start of the second half of the season. We had an encouraging race in Hungary leading into the summer break, and we now feel refreshed and determined to continue improving our form as the rest of the season progresses.
"We've persevered through some tough moments, but the positivity and steadfast commitment to McLaren-Honda's future success are evident in every single member of this team. Our drivers, too, have been unwavering in their support and are working hard to keep pushing us forward, extracting the maximum from the package at every opportunity. We're also incredibly grateful for the support of our partners, who are incredibly loyal, and who are united behind our development programme. In the second half of the season, our fight towards the front will continue, and we'll work hard to build on our steady, solid progress in pursuit of performance.
"Spa is a truly spectacular circuit - arguably the best on the calendar for many - but, given the unique power and downforce package required, the track won't play to our strengths. Therefore, of course, we must be measured in our optimism, and we will need to wait for Singapore and beyond before we can see the fruits of our labours reflected on track."
Yasuhisa Arai, Honda R&D senior managing officer - chief officer of motorsport: "After a well-deserved and positive result in Hungary, the summer break was good rest for the trackside team, while Sakura continued on with the power unit development.
"As we planned, Honda has updated our combustion characteristics to further improve our power units for Spa and the second half of the season. This weekend's free practices will be important to test the pairing of the power units to the cars. The Belgian race, however, will surely be a difficult one for the team and drivers, with expected grid penalties and a long and unforgiving power circuit.
"Nevertheless, McLaren-Honda's focus is to improve race by race. We know we can learn a lot from the circuit for immediate future, and hope that we can come out of the weekend with some positives."
Technical words of wisdom from Matt Morris, director of engineering: "Spa-Francorchamps is one of the classic old-school circuits. It's long; it's undulating and it's high-speed - all of which combines to make it one of the great challenges on the calendar. There are two high-speed sectors, in which there are long periods of full throttle, and one twistier sector. Car set-up is therefore a compromise between straight-line speed and cornering grip, and getting that balance right is a challenge.
"This is also a race at which you need to think on your feet because the weather is notoriously unpredictable. The conditions can change very quickly, which usually spices things up!"