Since the Formula One World Championship era began in 1950, 69 circuits have hosted at least one grand prix.
Some, like Spa-Francorchamps, Silverstone and Monza, stand out as true jewels in the sport's crown. Modified over the years to keep up with the changing face of F1, these circuits never lost their character.
Others, like AVUS, Phoenix and Valencia, never had any to lose.
And in between we encounter the likes of Watkins Glen, the Osterreichring and Suzuka—all great motorsports venues, but without the same lengthy F1 history as their more illustriously considered peers.
How on earth do we even begin to rank them all?
In this article, I've started with the number of races the circuit has held. This figure is then multiplied by what I've called "F1 Factor"—a score out of 20 based on a number of things including layout, historical significance and quality of racing—to reach a final ranking score.
This score is then used to rank the circuits in terms of their overall contribution to the history of F1.
Using this formula, here are the top 25 F1 circuits of all time.
This is a score out of 20. Half is made up of a rating out of 10 on the quality of the track layout. A maximum of five points were awarded to each for their historical significance, and a further five for the quality of racing they have produced over the years.
Where more than one layout was used, the layout and racing scores are a rough average. For example, the old Nurburgring would easily have scored full points, but it was dragged down a little by the new one.
By necessity, circuits only in use a long time ago, before the era of full TV coverage and masses of footage were rated using race reports, track maps, witness accounts and other available information.
Races: 13. F1 Factor: 15.
Autódromo do Estoril was built in 1972, and first hosted the Portuguese Grand Prix in 1984.
Estoril tended to produce exciting races, and its Parabolica was one of the best in F1. Few fans who saw Jacques Villeneuve overtake Michael Schumacher around the outside at this corner in 1996 ever forgot it.
The circuit could still be hosting races today, and they'd probably be good races. Unfortunately, the track owners were sloppy with safety upgrades and this resulted in the 1997 race being cancelled.
But a return could be on the cards. Estoril was recently awarded FIA Grade 1 status, meaning it is of sufficient standard to host the Portuguese Grand Prix again.
Whether that will happen or not remains to be seen.
Races: 11. F1 Factor: 18.
Most street circuits exist because the organisers want a venue that looks pretty on TV, or because they want something different.
But the Adelaide Street Circuit existed simply because it was a really good race track.
The first Australian Grand Prix was held at the circuit in 1985, and it was everything a street circuit should be. The usual 90-degree corners were offset by a wide variety of fast and slow corners, and overtaking was never a problem.
Many a sad, salty tear was shed when the race moved to Melbourne in 1996. But F1 in Adelaide could not have carried on forever.
The problem was that faithful old chestnut, safety. It wouldn't pass the strict standards required of circuits today without huge changes to the layout, which would almost certainly destroy its character.
Adelaide only held 11 race, but was arguably the sport's best ever street circuits.
Races: 18. F1 Factor: 11.
Circuit de Nevers Magny-Cours made its F1 debut in 1991, the ninth circuit to host the French Grand Prix.
The race stayed there until France disappeared from the calendar in 2008.
On paper the circuit doesn't look too bad. The fast chicanes should be interesting and there's a long straight with a hairpin at the end, so current theory suggests overtaking should be common.
Sadly, F1 races don't take place on paper, and Magny-Cours was brilliant at producing dull races. Modifications were made in 2003 in an attempt to improve the spectacle, but nothing really changed.
Only one French Grand Prix at the venue sticks in the memory, the rain-affected 1999 race.
F1 is unlikely to return.
Races: 14. F1 Factor: 15.
Circuit Paul Ricard holds the distinction of being the only F1 circuit named after the man who paid for it—pastis tycoon Paul Ricard.
It was built in 1969 and first hosted the French Grand Prix in 1971. The event moved around a lot in those days and, by 1985, Paul Ricard had hosted it eight times.
The original layout featured a number of high-speed corners and the gigantic 1.8-kilometre long Mistral Straight. As with most circuits of its age, safety was its undoing.
In 1986 Elio de Angelis was killed in a testing accident, and the track was drastically shortened.
Paul Ricard became a shadow of its former self, holding the French Grand Prix a further five times before Magny-Cours took over in 1991.
In recent years the circuit was bought by Bernie Ecclestone and rebuilt as a test facility. Now officially known as Paul Ricard High Tech Test Track, its brightly coloured run off areas have transformed it into one of the most hideously ugly places in the solar system.
If F1 ever returns, they're going to need a huge paper bag...
Races: 20. F1 Factor: 11.
Built in 1952 as Autodromo 17 de Octubre (a significant day for then-President Juan Peron), this circuit in Buenos Aires first hosted the Argentine Grand Prix the following year.
After a transmission failure in the first event, home hero Juan Manuel Fangio won the race four times in a row between 1954 and 1957. After seven races, it disappeared from the calendar.
It came back in 1972, using a different layout (No. 9—the first had been No. 2). Two races later it switched to yet another layout (No. 15), hosting seven races before Argentina invaded the Falkland Islands and the 1982 event was cancelled.
This classic boomerang story continued into the 1990s. Layout No. 6 hosted four races, the last of which was in 1998.
Few tears were shed when it didn't make the calendar in 1999. Of the four layouts used, only No. 15 was any good, and the last one (No. 6) was the worst of the lot.
There are no signs F1 will be back.
Races: 18. F1 Factor: 13.
The Melbourne Grand Prix Circuit in Albert Park (the name by which it's more commonly known) first hosted the Australian Grand Prix in 1996, but its racing history goes back a long way.
A circuit almost identical to the one used today hosted two non-championship races in the 1950s.
It tends to produce exciting races, but that's usually because it's among the opening races of any given season. And while the location is stunning, the circuit is flat and somewhat bland.
Taking over from a much-loved venue like the Adelaide Street Circuit was never going to be easy.
But at least Albert Park has a few challenging corners, and it's the perfect type of track at which to kick off a new season.
Races: 14. F1 Factor: 17.
Brands Hatch started life as a dirt track way back in the 1920s, but the tarmac course was laid down in the 1950s.
It hosted the British Grand Prix for the first time in 1964, and alternated with Silverstone until 1986. In addition it hosted two European Grands Prix, in 1983 and 1985.
Blessed with a stunning natural amphitheatre setting, Brands boasted some spectacular corners and was a favourite with the drivers. The highlight then as it is now was Paddock Hill Bend, an absurdly steep downhill right-hander at the end of the pit straight.
Sadly, the circuit was just too small and cramped. Cars were becoming faster and safety requirements were rising, so 1986's race was the last time F1 visited Brands Hatch.
It's unlikely to ever return.
Races: 15. F1 Factor: 16.
Located in the urban heart of sprawling Mexico City, the Autodromo Hermanos Rodriguez arrived on the F1 scene in 1963. Then called Magdalena Mixhuca, it remained on the calendar until 1970.
That race was marred by crowd trouble, and defending world champion Jackie Stewart was forced to retire after hitting a dog on the circuit.
The following year's race was cancelled, but F1 returned in 1986. The track had been shortened slightly and the safety featured had been greatly improved.
But it was increasingly bumpy, and the crowding problems never entirely went away. No race was scheduled for 1993.
In recent years talk emerged of bringing the Mexican Grand Prix back, and it looks set to happen in 2015.
The renovated Autodromo will again be the venue.
Races: 15. F1 Factor: 16.
The Sepang International Circuit was the first of the new breed of circuits that now dominate F1. Designed by Hermann Tilke, it first hosted the Malaysian Grand Prix in 1999.
New, ultramodern and featuring some magnificent corners, Sepang received universal praise. The drivers loved it because it provided a genuine challenge and most fans were in agreement that it was a very good track.
Little has changed since then. As more and more Tilke creations are added, Sepang continues to stand out as one of the best circuits on the calendar.
With Turns 1, 5 and 6 among the highlights, it's arguably his best creation to date.
Not everything gets better with age.
Races: 20. F1 Factor: 15.
After three races in the confusingly named East London, the South African Grand Prix moved to Kyalami in 1962.
The original circuit was one of the fastest on the calendar, and home to the race until 1985.
F1 had to this point resisted mounting international pressure to boycott South Africa due to the apartheid regime, but eventually the powers-that-be caved in. The 1986 race was cancelled.
It was slower and tighter than the old course, and the reborn race never really took off.
After just two years, F1 departed. A return is unlikely.
Races: 28. F1 Factor: 11.
It was considered quite a coup when Bernie Ecclestone announced F1's first race behind the Iron Curtain would take place in 1986. The Hungaroring, in then-communist Hungary, was the venue.
With the entire state behind them, the designers could have created something special.
Instead they made a slow, twisty little track without a single notable corner.
It's not all bad. The elevation changes add interest and the non-stop string of corners provides a real challenge for the drivers.
Changes in 2003 made overtaking slightly more of a possibility, and the proliferation of ultramodern circuits means the Hungaroring is one of an ever-shrinking number of old-style tracks.
But F1 seems to have outgrown the venue. As the sport pushes more and more to improve the spectacle, this circuit may be left behind.
Races: 23. F1 Factor: 14.
The Circuit de Catalunya first hosted the Spanish Grand Prix in 1991. It instantly produced a memorable moment, as Ayrton Senna and Nigel Mansell had their thrilling side-by-side duel down the main straight in the circuit's first-ever race.
The drivers and teams appreciated its exciting mix of slow, medium and high-speed corners; it quickly became a popular venue for testing.
Sadly, it doesn't produce good races anymore.
As aerodynamics became more and more important in car performance throughout the 1990s, drivers could no longer follow closely through the final sector and were too far behind to challenge on the pit straight.
Changes were made in 2007 in an attempt to remedy this, and DRS has helped too.
But a larger redesign is needed for Catalunya to ever consistently produce good races again.
Races: 20. F1 Factor: 17.
The roads around the village of Watkins Glen had hosted motorsports events as far back as the 1940s, but the circuit fans know and love was laid down in 1956.
It hosted its first United States Grand Prix five years later, in 1961.
The race at The Glen quickly became a key fixture in the F1 calendar, attracting large crowds and giving the sport a true home in the United States.
But as the cars became faster and more advanced, concerns over safety grew as well. Modifications were made, but they only delayed the inevitable.
The 1980 race was the last to be held at Watkins Glen. In the years that followed F1 embarked on an increasingly desperate tour of substandard venues as it sought a new home in the world's largest market.
Austin's Circuit of the Americas appears to have finally ended that search, and F1 once more has an American base at a quality venue.
It only took 32 years.
Races: 27. F1 Factor: 15.
Officially known as the Autodromo Internazionale Enzo e Dino Ferrari, Imola hosted the Italian Grand Prix for the first and only time in 1980.
The following year it was awarded its own race, the San Marino Grand Prix (named after the nearby country because there was already an Italian Grand Prix). The race was held every year until 2006.
For many, Imola is remembered for one dark weekend in 1994. Rubens Barrichello suffered a nasty accident in practice on Friday and was lucky to escape without more serious injury.
In qualifying the next day, Austrian driver Roland Ratzenberger lost his life in a heavy crash at Villeneuve. And in Sunday's race, Ayrton Senna died after going straight on at Tamburello.
Changes were made to the circuit and when F1 departed in 2006, it left a very different Imola behind.
The track has been upgraded further since then, and a return is not out of the question.
Races: 25. F1 Factor: 17.
This circuit started life in 1969 as the Osterreichring, hosting the Austrian Grand Prix for the first time the following year. It was one of the most beautiful tracks F1 has ever seen, rising and falling though the Styrian mountains in Austria.
Sadly, it was sorely lacking in safety features. High-speed corners dominated, with little in the way of run-off or protection from the scenery.
Somehow it survived in a form almost identical to the original layout until 1987, when it hosted its last race.
A decade later, F1 cars returned to Austria and found a very different circuit waiting for them. Now called the A1-Ring, the new track was a shorter, slower, sterile version of the old beast that once occupied the same spot.
But somehow, the little seven-corner circuit worked. Enough of the old Osterreichring's beauty was retained and races tended to be better than average.
It was Hermann Tilke's first full-circuit design, and one of his best.
F1 departed in 2003, but will return in 2014.
Races: 25. F1 Factor: 18.
Built as a Honda test track in 1962, Suzuka hosted its first Japanese Grand Prix in 1987.
It instantly became a favourite of fans and drivers alike, and its usual place toward the end of the calendar has led to 13 world champions having been crowned here—some more controversially than others.
Suzuka was famously the scene of two of the most unsavoury championship deciders in F1 history. In 1989 Ayrton Senna and Alain Prost collided at the chicane, and Prost took the title.
The following year they clashed again, and this time the title went to Senna.
Suzuka is a rare example of a circuit that has stood the test of time. Even the trained eye struggles to spot the differences between the current layout and the one on which the first race was held.
It actually punishes mistakes, a rarity in the modern era.
The Esses section is one of the finest sequences in the motoring world, and corners like Spoon and 130R stand out as highlights.
Races: 30. F1 Factor: 17.
Built a stone's throw from the sea on the northern coast of the Netherlands, Zandvoort first hosted the Dutch Grand Prix in 1952.
Like many circuits of the day, it was a fast, flowing layout with few safety features. In the early decades this was accepted, but in 1972 the drivers refused to race at Zandvoort, deeming it too dangerous.
Improvements were quickly made and the circuit returned to the calendar the following year. But despite the improvements, Zandvoort was always on borrowed time.
It held its final race in 1985.
Part of the track was sold, and a new layout now graces the sand dunes—but F1 is unlikely to return.
Races: 33. F1 Factor: 16.
Hockenheim was constructed in the 1930s in the forests of Baden-Wurttemberg, and a cut-down version of the original layout first hosted a German Grand Prix in 1970.
The circuit was simple but effective—most of the 6.8-kilometre (4.2-mile) circuit was made up of four long straights linked by three slow chicanes. A tight "stadium" section at the end of the lap added some variety.
With a huge distance between one end of the circuit and the other, it was common for rain to be falling in some sections while others were bone dry.
Hockenheim survived in this form until the early 2000s, but the F1 world was pushing for higher and higher safety standards, and eventually it had to be changed.
A redesigned Hockenheim made its debut in 2002. The long, fast loop through the forest was put out to pasture and the overall length cut to 4.6-kilometres (2.8-miles).
The new layout isn't terrible, but it's not especially good either. Hockenheim no longer stands out as a special circuit—an unfortunate but necessary victim of modern F1.
Races: 31. F1 Factor: 18.
The Autodromo Jose Carlos Pace, more commonly known as Interlagos (its original name, but one which it lost in 1975), held the first ever Brazilian Grand Prix in 1973.
The version used for that race was one of the most tightly packed circuits F1 has ever seen. At a shade under eight kilometres in length, it was left behind by the more demanding safety standards of F1.
Its final race was in 1980, but we hadn't seen the last of Interlagos.
In 1990, the new cut-down version hosted its first race. It retained much of the old, undulating layout, including the uniquely kinked pit straight, and added what is now known as the Senna S.
There aren't many beautiful chicanes in the world, but this is one of them.
Interlagos is one of the F1's few remaining jewels. Hopefully it will remain on the calendar long into the future.
Races: 34. F1 Factor: 18.
Perched upon the man-made Ile Notre Dame in the St. Lawrence River, Montreal, the Circuit Gilles Villeneuve is one of modern F1's most dearly beloved venues. Since it was first used in 1978, no other circuit has held a Canadian Grand Prix.
Its beauty lies in its simplicity. Though it once had a slightly more complex layout, the current track is essentially two hairpins connected by a few chicanes and some long straights.
It doesn't sound like much, but it works.
No circuit on the current calendar is as good at consistently producing great races. Overtaking has always been possible (though DRS has perhaps made it too easy in recent years), and close racing is almost guaranteed.
Montreal is proof a circuit doesn't need a "perfect" mix of corner types and artificially crafted overtaking zones.
Hermann Tilke, take note.
Races: 40. F1 Factor: 18.
In the early days of F1, it wasn't uncommon for races to be run on public roads. Such circuits tended to be long, fast and dangerous—and the Granddaddy of the them all was the Nurburgring's Nordschleife (northern loop).
Over 22 kilometres (14 miles) in length, the Nordschleife featured jumps, banking, blind crests and 160 corners. F1 has never seen a greater test of man and machine, and it never again will.
But with the challenge and sheer size of the place also came danger. As the sport progressed into the 1970s, the risk of racing here was deemed unacceptable. Changes were made to improve safety, but they weren't (and could never have been) enough.
The German Grand Prix of 1976—in which Niki Lauda was badly burned and almost lost his life—was the last F1 race held on the Nordschleife.
In 1984 a new circuit hosted the German Grand Prix, the Nurburgring GP-Strecke. Tacked onto the southern edge of the Nordschleife, the new circuit was built to conform to modern safety standards.
It was also a little bit sterile and bland. Changes have been made over the years in an attempt to improve the spectacle and it's better than it was, but the GP-Strecke will never match up to its big brother.
Races: 47. F1 Factor: 19
Silverstone hosted the first-ever race of the world championship era, all the way back in May 1950. Since then it has held the British Grand Prix 47 times.
The land upon which the circuit lies started life as RAF Silverstone, a training base for British air crews flying the Wellington bomber. Opened in 1943, it was used until the end of World War II.
When hostilities ceased the aircraft departed and the airfield's perimeter road was put into service as a race track.
Silverstone's overall shape has changed little, but numerous corners and chicanes have been added and changed over the years, mostly in the name of safety.
Fortunately, the character of the place has always been retained, and the Maggots-Becketts-Chapel complex stands out as one of the best quick corner sequences in the world.
Fast and flowing, Silverstone remains a favourite of drivers and fans alike.
Races: 46. F1 Factor: 20.
The modern Spa-Francorchamps circuit bears only a passing resemblance to the fearsome old beast that once hosted grands prix.
But unlike so many other cut-down modern tracks, Spa managed to retain its charm and majesty.
The old layout was a 14.1-kilometre (8.8-mile) blast around the Belgian countryside. It was always dangerous, and as F1 moved forward the circuit was left behind. Old Spa hosted its final F1 race in 1970.
New Spa made its F1 debut in 1983. A smaller circuit, it retained famous corners such as Eau Rouge, Blanchimont and La Source while adding the quite lovely Pouhon.
Increasing downforce levels have made once-difficult corners easy, but Spa is still the best F1-standard circuit in the world.
Races: 61. F1 Factor: 18.
Held around the streets of the world's second-smallest country, the Monaco Grand Prix has taken place 61 times in the world championship era.
It's the last true, old-style street circuit in F1. The roads it runs on were designed primarily for everyday traffic, with little consideration given to the sport. And it shows—the circuit is totally unsuitable for the cars of today.
There's little room for modern safety features, the straights aren't long enough and races are usually dull processions.
But it's allowed to exist simply because it's Monaco. It has glamour, prestige and (perhaps more importantly these days) everyone has heard of it, whether they know what F1 is or not.
And from a fan's point of view, when an overtake does occur, it's usually pretty special.
Races: 63. F1 Factor: 18.
Since the start of the world championship era, no circuit has hosted more grands prix than Monza.
Located in the city of the same name, a few miles north of Milan, this track started life in 1922. The layout back then incorporated a banked oval, but the rest was almost identical to the circuit we see today.
Chicanes have been added and some turns have been slightly re-profiled, but drivers of every era negotiated corners such as Curva Grande, the Lesmos and Parabolica.
And if the history wasn't enough, Monza is also the spiritual home of the tifosi, who make up one of F1's most passionate, knowledgeable crowds.
It doesn't match up to a circuit like Spa in terms of sheer beauty and challenge, but Monza is still a worthy No. 1.