Twice a year Spain is brought to a virtual standstill when its two biggest clubs cross swords in the league, the media shamelessly billing every encounter as the "game of the century".
The nationalistic, political and cultural rivalries that suffuse "el clasico" ensure it is one of the most intensely disputed fixtures in world sport.
What makes this season's clash more special than most is that for the first time in years the two teams are locked in combat at the top of the table.
After five barren seasons in which they failed to challenge for the league title, Barcelona have finally reclaimed their status as the chief rivals to Real Madrid in a restoration of Spanish soccer's traditional duopoly.
Barca last won the championship in 1999 under Dutchman Louis van Gaal, but since then they have been toppled from their pedestal as the more modest Deportivo Coruna and Valencia took up the challenge against Real.
One reason for the Catalans' decline was the body blow dealt to them four years ago when the newly-elected Real president Florentino Perez made off with their best player Luis Figo.
The world-record $56 million that Perez paid to spirit away the Portuguese midfielder was frittered away in a flurry of rushed transfer deals by Barca's new president Joan Gaspart that did nothing to compensate for his departure.
The vitriolic reception accorded to Figo when he has returned to the Nou Camp gives some indication of the depth of resentment caused by their idol's desertion to the enemy.
WORLD'S BEST
Traumatised by the loss of Figo and undermined by a series of power struggles as his rivals jostled for position behind his back, the over-emotional Gaspart was constantly outmanoeuvred by Perez who proceeded to bring some of the world's top players to the club.
Zinedine Zidane, Ronaldo and David Beckham followed Figo to the Bernabeu in a succession of big money moves financed by the sale of Real's city centre training ground to a compliant local authority that threatened to eclipse anything done by their rivals.
But although they have constructed one of the most glamorous football teams in the history of club football, Perez's policies have not reaped the spectacular trophy haul that many forecast.
Admittedly, Real won the league title in 2001 and followed that up with a ninth triumph in the European Cup, but since then their only major trophy has been the league title in 2003 which they only managed to win after unfancied Real Sociedad choked in the run-in.
Perez's "Galacticos" super-team may have been a dream come true for the Real marketing men, but his recruitment policy led to the creation of an ageing, defensively frail outfit that imploded so spectacularly in the final stages of last season.
While the cracks appeared in Perez's project, the pendulum began to swing in favour of his new opposite number Joan Laporta.
Laporta made a none too auspicious start at Barca before the start of last season when he failed to honour his electoral pledge to sign Beckham, but that setback ended up being a blessing in disguise.
Instead of Beckham, the Catalans got Brazilian forward Ronaldinho, a player who has almost single-handedly restored morale amongst the club's fans.
The buck-toothed former Paris St Germain forward may have been a distant second to Beckham in marketing terms, but as regards football his electric performances on the pitch have put the England captain in the shade.
REVIVAL
Together with mid-season signing Edgar Davids, Ronaldinho sparked a remarkable Barcelona revival that saw them recover from a terrible start to overhaul Real Madrid and grab second place behind Valencia in the title race.
Buoyed by their best finish in four years, Barcelona took the transfer market by storm in the close-season with the addition of some of the most in-form players on the continent, including Deco, Ludovic Giuly, Henrik Larsson and Edmilson.
Laporta even managed to get one over Perez by winning the tug-of-war for African Player of the Year Samuel Eto'o, who was part-owned by Real and who the president claimed would never play for the Catalans.
To rub salt in the wound, the fiery Cameroon striker is the leading scorer in the Spanish Primera Liga this season with nine goals and it has been Barcelona who have been playing the sort of breathtaking, attacking football that Perez claimed was the monopoly of his Galacticos.
Of course it is still too early to write Real off, as their 6-1 win over Albacete at the weekend showed.
They may not have produced the stylish football of a few seasons ago, but the addition of Argentine centre back Walter Samuel has made them a little more steady, while the purchase of Michael Owen has added more options up front.
Barca remain the better balanced side, but their first-round exit from the Spanish Cup and last week's defeat at Real Betis show they are far from invincible and, in any case, the form book counts for very little in a game like this.
All that can be guaranteed is that whatever happens, Saturday's match at the Nou Camp will remain a talking point in Spain until the next "clasico".
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