Barcelona and Real Madrid are two of the richest, successful and iconic football teams on the planet. Combined, they have 59 top flight titles - Real Madrid with 33 and Barcelona 26 - and have won the Champions League on 18 occasions - Real Madrid with 13 and Barcelona five.
So the rivalry is effectively two world class teams battling it out to be the best side in Spain, right?
It's not quite that simple.
The rivalry transcended sport some time ago.
El Clasico is the battle of two modern, cosmopolitan cities. That's something we can all agree on.
Unfortunately, the pair disagree on just about everything else.
Over 600km separate Barcelona and Madrid, but culturally and politically they are worlds apart. Real Madrid represent Spanish nationalism, while Barcelona represent Catalonia and Catalan culture. Madrid are traditionally viewed as the more right wing, conservative club, supported by the royals, while Barcelona are more left wing and anti-establishment.
These differences really began to take shape in the 1930s following the Spanish Civil War. Nationalist dictator Francisco Franco seized control of the country in 1939, and attempted to oppress and ban Catalan language, culture and identity.
Real were perceived as Franco's team, representing traditional Spanish culture and the power of centralised Spain, while Barcelona were the plucky underdogs, persecuted by Franco's regime.
There are tales of Franco exerting his influence to Barcelona's detriment on the pitch, too. In 1943, Barcelona beat Real Madrid 3-0 in the first leg of a cup semi-final. Before the second leg, Franco’s director of state security popped by to remind the Barça players that they were only lucky enough to play thanks to the sheer generosity of the regime.
Real won the second leg 11-1.
Franco is also rumoured to have flexed his muscles to help Real acquire Alfredo Di Stefano in 1953, when Barcelona had just agreed to sign the Argentinian. Di Stefano went on to guide Real to five European Cups.
Franco has been in his grave for a good 45 years, but with Catalan's independence movement continuing to rage, the rivalry never strays too far away from politics - the first Clasico of the 2019/20 season had to be postponed due to political unrest in Catalonia.
Di Stefano's move to Real was a good 67 years ago, but controversial transfers continue to stoke the rivalry's flames.
In 2000, after five years at Barcelona, Luís Figo controversially switched allegiances, moving to Real Madrid for €62m. Barcelona fans are not renowned for being the most hostile fans in world football, but they made an exception for Figo’s return.
Banners bearing the words ‘traitor’ and ‘Judas’ decked Camp Nou, missiles were flung in his direction and Figo was taken off corner duty to prevent him getting too close to the furious Barcelona supporters.
Figo is one in a long line of world class players to have taken to the field during El Clasico while at the peak of his powers, and it is on the football pitch where the Barcelona versus Real Madrid rivalry really thrives.
A collection of the finest players to ever grace the game have lined up on opposite sides throughout El Clasico history - Lionel Messi, Xavi, Andres Iniesta, Ronaldinho, Maradona, Johan Cruyff, Cristiano Ronaldo, Raul, Zinedine Zidane, Ferenc Puskás, Ronaldo, Roberto Carlos - the list is bottomless.
This makes for an absolute blockbuster of a fixture, capturing a huge global audience. There is often so much riding on the game with regards to the title race - the pair have won 14 out of the last 15 La Liga titles. The longevity of each side's success is determined by how the other side responds.
The pair play off one another. When Figo left, Barcelona’s recruitment strategy adapted, and they began pooling more resources into their world famous La Masia academy. This strategy was at the core of everything they achieved under Pep Guardiola; huge global success thanks to a core of home grown talent.
Despite their differences, both Real Madrid and Barcelona each evolve as a result of the other.