If you watched it, you'll never forget it.
Ninety minutes seared on your consciousness, the memory of which will keep you warm on cold nights and bring colour to a month of humdrum days.
Unless you wear one of these two club's colours, let's set the result - a 4-3 away win for Barcelona - aside for a minute.
Football was invented for a night like this. Bravery, brio, technique, showmanship, nerve, fun, fear, fury - goals, goals, goals.
For my taste, neither side left the arena other than with its reputation enhanced. It's for others, tonight, to describe the goals and the glory. Here are some thoughts which this gargantuan display make me ponder.
1. What to make of Gerardo Martino?
Whether he wins the title (or anything else), whether he walks or stays, this likeable but puzzling Argentinian will always be able to point to a 100 percent Clasico win record in his first season, six goals scored and a continuation of Barcelona's pretty remarkable record of two defeats in their 10 visits to the Bernabeu prior to this win.
That's one hell of a calling card.
Personally, I'm also pleased for a guy who is evidently a decent man, articulate, liked by the great majority of his very demanding squad and, I'd say, a delight to deal with from a media perspective.
Martino has confirmed the age-old knowledge that all that glitters isn't necessarily gold. He has found life at the Camp Nou to be unforgiving, to be as comfortable as a scorpion in our underpants … to be politically unstable.
For a man who was enamoured, possibly dazzled, by the era of football he'd admired from afar, this has been like a bucket of ice cold water over the head. So, minimum, for him to take away two Real Madrid scalps means that his trip across the Atlantic has not been in vain.
Nevertheless, I'm skeptical as to how much this night advances either his learning trajectory or our judgement of his tactical nous. In attacking terms, his Neymar bet didn't work, regardless of whether you judge ref Alberto Undiano Mallenco right or wrong to have given a penalty and a red card that was, pretty much, the Brazilian's only useful moment.
Worse yet, Madrid utterly plundered Barcelona's right-hand side where the Brazilian's consistent choice to run into trouble and give the ball away was compounded by his lack of work, all of which allowed Marcelo and Angel Di Maria to double up on Dani Alves and, had Karim Benzema not fluffed more chances than he scored, practically win the game.
Furthermore, Martino retains an utterly unshakeable faith in Javier Mascherano as a central defender. Most of us had noted approximately two seasons ago that this is misplaced. The first two Real Madrid goals only served to emphasise that this intelligent, inspirational football leader is a recycled midfielder who can't jump, doesn't read penalty box situations well and will be exposed in elite level contests.
Even more than the actual result, adulterated by Lionel Messi's genius - what a pass for the Neymar-Sergio Ramos incident! - it's interesting as to whether Martino playing all four key midfielders in this match is a confirmation that he realises that it was a horrible, horrible botch-up not to do so in San Sebastián and Valladolid?
On the plus side, I keep returning to his key promise when he took over. That was to try to get as many of the central footballers in this squad in completely different physical and mental shape to that in which they found themselves against Bayern Munich and Real last spring.
If he meets that goal then he'll deserve a hell of a lot of kudos, and some apologies from the Catalan media.
In summary, this is a man whose football notebook has very different annotations from Pep Guardiola, Johan Cruyff, Xavi & Co. He's on a learning journey, one which has threatened to derail from time to time.
As for this game? This was evidence that while not finished yet, setting off on that journey was a worthwhile exercise.
2. What to make of Real Madrid?
Part of the reason that I decided to tip a single goal win for Barcelona? There had been a collection of small signs that the absolutely intense football Madrid have been producing since the start of January was presenting a bill to be paid.
Xabi Alonso's return to the team after the first Clasico this season coincided with a vast, sprawling veldt of wins and draws. Organisation, drive, inspiration. Class.
The 4-3-3 that Ancelotti has asked his players to enforce has been dynamic, well suited to their abilities and effective. But, I'd say, tiring.
For a decent spell in the Madrid 'derbi' before eventually taking charge, Los Blancos were on the back foot and began to make poor choices positionally. By the time they regained their composure, the 2-2 result didn't do their power-finish justice. But it was an early sign.
Against Levante there was some slightly unusual imprecision in finishing. Against Malaga, again Madrid seemed a little less energetic, not as voracious, and when Bernd Schuster's side raised its work rate and quality from the standards of most of the rest of the season, that was enough to make it a tough three points.
Schalke was a test which showed that in opting to start his best XI as often as possible, Ancelotti had left his next best four or five footballers just a touch short of match sharpness. Not by much, but you could see the need for Xabi Alonso, Sergio Ramos and Ronaldo to start that match.
Now, at what cost that decision? Benzema spent the week getting back to fitness after a collision with Ronaldo last week - boy, it was worth the work. But if he had been injury free all week, might it have been him who hit the hat-trick long before Messi did?
Pepe, Isco and Di Maria all had ailments of various types that brought raised temperatures during the week, not ideal preparation for a test of endurance and concentration like this.
There was times in this Clasico when Madrid looked like a behemoth. Confident, precise, quick, voraciously hungry and likely to score every five or six minutes. Then there were spells when Barcelona dictated, raised and lowered the tempo as they wished, "controlling" the evening as much as that was possible.
I'm still of the opinion that Madrid profile nicely as treble candidates and are likely to be extremely hard to beat in the Copa del Rey final. Equally, I think that they are a shoe-in for the Champions League semi-final. They have Borussia Dortmund's measure.
I think that this was a match in which Madrid were millimetres short in terms of freshness, concentration and that final burst of power that takes you to the tape ahead of the chasing pack. But not a requiem for Ancelotti's season.
3. What to make of Neymar?
Who'd have thought in that blitzkrieg spell between the 20th and the 35th minute when it appeared that Madrid had five or six men streaming down their left wing and that Gareth Bale, Ronaldo or more likely Benzema could score at will from a ball hoisted in from the line that it would end up with Neymar trying to cheer up a miserable, red-eyed Marcelo by the final whistle?
Only Neymar's dad (and his bank manager) could genuinely say that there was anything in his performance to justifying him having started. But this is not to criticise Neymar the footballer. He has established already this season that there's quite a talent in there waiting to mature.
What he's also established, clearly, is that he has some gym work to do.
His upper body strength and his acceleration - given that he has been given basic natural speed as a birthright - aren't good enough to turn him from a fine player into a great one.
As I wrote this week, he could do a million times worse than learn lessons from Iniesta. Equally talented and once very slight, the Spaniard is now immensely strong, his winning mentality is fully engaged all season every season and he's every millimetre the champion, both as a man and as a footballer. And wasn't that one heck of a way to score his first Clasico goal?
Where I'm bemused, given that it's quite clear that Neymar has been both shrewd and likable enough to gain Messi's appreciation, is how slow he is at learning the rules of this team.
His two worst flaws against Madrid were repeatedly allowing Marcelo and Di Maria to completely overload Alves (already not the most assiduous marker) and, also, choosing over and again to dribble himself into a situation where he was robbed of the ball and a Barcelona attack suddenly became a Madrid counter. If Pep Guardiola got hold of this guy he'd have "THAT IS A CARDINAL SIN!" tattooed on his soul within 12 hours.
Neymar is going to be worth waiting for, I'm pretty sure. But an automatic starting place because of his price, his inflated cost and the weight of expectation from the Barcelona board? I don't think so.
4. What to make of the referee?
Cristiano Ronaldo, after the match: "The referee was white as a sheet, very nervous and he committed many errors. It obviously bugs certain people if Madrid are successful and winning. We needed a referee of the right stature for this game. I've been here for a long time and it seems to generate a lot of envy if we are doing well. People wanted Barcelona back in the title race and now they have that. We aren't treated equally."
That's what Ronaldo makes of referee Undiano. Even though the penalty that Ronaldo scored was a foul but committed outside the box. Perhaps Madrid's best player can be forgiven a little surge of adrenalin after a match like that.
Was Undiano really so bad? Was he biased? On the key decisions I'd say he comes off with a mixed record, but overall perhaps he still gets pass marks.
I've already said that even after replays, I'm unsure what level of contact there was between Ramos and Neymar and it's one heck of a punishment to concede a penalty and a red card at that stage of the match. But if the ref was utterly sure that Ramos made contact, then both decisions followed like lemmings follow the call off the cliff top every year.
Ronaldo's 'penalty' should have been a free kick, no more. But at that pace and with the favourable break they had at the Etihad Stadium in the Champions League when Martin Demichelis fouled Messi. Barcelona just need to roll with the blows.
The third penalty, in my view, is clearest. Dani Carvajal doesn't foul and Alonso's first try at Iniesta isn't one either. But the World Cup winner's knee into Iniesta's thigh is a foul anywhere else on the pitch and, thus, a penalty.
Undiano handled the scuffle between Cesc Fabregas, Pepe, Marcelo, Ramos and Jordi Alba perfectly well after Messi's first goal. Not having seen the moment when still images seem to show Sergio Busquets standing on Pepe's face, there are two things to say. If it was deliberate it's a straight red and a long ban. Secondly, not having seen it in real time, it's feasible that the referee did not either. Endless post-match television repeats may yet have something to say about that incident.
His interpretation of the majority of the 'ball to arm' decisions from free kicks (i.e. that they weren't penalties) seemed pretty good to me. Where I'm unconvinced is that appointing the same guy to referee three straight Clasicos - last season's Copa semi-final second leg plus the past two Liga meetings - is a shrewd idea.
Madrid left the last match bitterly angry at not having been given a 'stick on' penalty by Mascherano on Ronaldo. They had a real good case then. They brought that anger and mistrust into this game. Giving the same ref another of these games didn't help him, the players whose grudges were held or the game itself.
That said, his work wasn't the worst on the night. Not perfect and open to question, but not biased.
5. What to make of the run-in?
And now, the end is near. I'll state my case, of which I'm certain. Barcelona have the best Liga run-in.
While I'm not going to contradict my argument that Real still have the power and the quality to remain credible treble candidates, it's going to be absolutely fascinating as to how they deal with two of their next three matches being away at dangerous sides like Sevilla and Real Sociedad.
If they hurdle them, then major kudos to Real. Short-term, however, Barcelona don't have ties like that nor like Atletico's interesting matches at the San Mames and Mestalla.
Moreover, should it all go down to the last weekend, though the reigning champions have to face a difficult test in Atletico it's better to have your fate in your own hands, particularly at home.
What Madrid will be quietly pleased about is the fact that the Catalans and Atletico need to do potentially draining and difficult battles with each other twice more in order to produce a Champions League semi-finalist.
Ladies and gentlemen, we still very much have game on!
Graham Hunter covers Spanish football and FC Barcelona for Sky Sports, the BBC, ESPN and a number of newspapers and magazines across the world. He is also the author of Barca: The Making of the Greatest Team in the World. You can follow him on Twitter @bumpergraham