Late in the afternoon the sky blackened and it started to rain. In the hotel where Athletic Club Bilbao were preparing, a player glanced out of the window, looked back at his team-mates and said: "Good." That's the way it has always been, according to José Angel Iríbar, captain, goalkeeper and icon, the man who took the still-illegal Basque flag on to the pitch with the Real Sociedad captain Inaxio Kortabarria before the derby in 1976. It is also the way it is supposed to be. It felt right. Without rain, it wouldn't be San Mamés and tonight, more than any night, what they most wanted was for it to be San Mamés.

San Mamés was Athletic Club's home for 99 years and 11 months and it was unique, the oldest ground in the league. They called it the Cathedral, a place of worship and liturgy like no other; a place that drew you in along Licenciado Poza, straight and narrow and lined with bars, red and white flags hanging from their doorways, black and white photos hanging from their walls. At the end of the road stood the side of the stadium painted with the Athletic badge, bold against the white wall.

It is not there now. On Monday night, at the end of the road stood a strip of corrugated iron. Towering over it, a mound of earth with a digger sitting triumphantly on top. And towering over that, 50 metres or so away, a bright light. The light came from the new San Mamés and it was made brighter, more enticing, by its shape. One end of the new stadium is yet to be built; three sides, shaped like a horse shoe, open up on the site of the old San Mamés. But for that corrugated iron you could keep going along Licenciado Poza, walking into the light until you ended up on the pitch. The playing surface has rotated and moved, but not far. Fifty metres, maybe. Perhaps a hundred.

The end behind one goal will occupy what was the main stand, where a stuffed lion prowled the directors' box and the bust of the club legend Pichichi stood, presented with flowers every time a new team visited (the last time was when Arsenal Ladies came). For now it is occupied by dozens of diggers and cranes. At the end of the new pitch stands a makeshift wall made of scaffolding and red tarpaulin.

The original San Mamés was inaugurated in August 1913 against Racing Irún. Just over 100 years later, the new San Mamés staged its first game, against Celta de Vigo. It has cost €173m and has been built in only two years. Kutxabank and the Basque government have paid €50m each, the provincial Diputación too, while Athletic paid €33m and the Bilbao council €11m.

Athletic departed San Mamés at the end of last season; the new stadium was being built around it. As the season ended the old one was demolished. This season started with a "home" game at Real Sociedad's Anoeta, 20,000 fans travelling more than 100km to see them face Osasuna. Now, after one game away, they were back. Not quite back where they have always been but almost.

On Friday, Athletic staged a training session there, attended by 10,000 people. On Monday, it was unfinished but it was ready for use: when it is done, in just over a year's time, it will hold 53,000; on Monday night it held 36,700 and it was packed. There is no room for away fans and no room yet for new season ticket holders. There will be more than 41,000 of them, up from 34,373. Fans are already paying a subscription to have the right to membership when the ground is ready for them, too.

The famous arch from the roof of the old San Mamés is no longer visible – it has been deconstructed and the plan is for it to be rebuilt piece by piece at the club's Lezama training ground – but from the river, the new ground rises up. There is something of the Emirates about it: steep stands and red seats, as steep and as close to the pitch as Uefa rules allow. Athletic will ask to host games at the 2020 European Championship. The outside of the stadium is lit up by panels and the roof reaches across the stands, all the better to keep the noise in and the fans dry. Officially 2,700 fans will get wet when it rains and they get a 50% discount on their season ticket prices: last night suggested that it will be rather more than that. It is a superb arena, the view spectacular and the noise loud.

It was a big night. Before the game, Celta's manager Luis Enrique stood at the mouth of the tunnel and pulled out his phone, taking pictures. But would it be San Mamés? That was the obsession. The reality is that the old San Mamés was crumbling and from the back of the lower stand you could not see the ball if it went in the air, but it had something. Invariably described as the most English of grounds, it smelt of cigars and grass, of football. No ground said tradition like it. Few sensations matched standing in the centre of the pitch there when it is empty, the silence almost reverential.

"The future starts here," declared one headline on Monday morning. The question that occupied everyone was whether it would feel the same, whether the past would accompany it, that sentiment and feeling, the identity. That, and whether the team would be up for it. "We're playing for far more than three points," said the coach Ernesto Valverde.

Andoni Ayarza, writing in El Correo, insisted: "this is not just a stadium, it is a symbol of a glorious past that constructs a bridge to a new future." The excitement was palpable but the fear was that it would not be quite right and that they would suffer a kind of Maracanazo of their own. Valverde said that he had encouraged his team by stressing to them the significance of the moment, but would it get to them?

They need not have worried. Was it San Mamés? Yes … and no. Not yet, not quite. And yet at the same time it was unmistakably Athletic. The atmosphere was superb, the noise loud, the obsession with acoustics well served, even if there were moments when it felt like they didn't want to let go entirely, as if that would be somehow wrong, maybe a little unfaithful to the old Cathedral, still there behind the wall at the open end.

That will surely come; in fact, it was there on Monday night. Athletic may have moved stadiums but it will do them less harm than it might others: few clubs have protected their identity, their history and traditions as they have.

And besides, those doubts are minor and the opening night was a huge success. "The dream debut," declared the Correo Vasco on Tuesday morning. Deia called it "San Mamés's triumph". AS hailed "the same fight as always". "The legend is reborn," cheered Marca. It was, it added, "a fiesta total".

The pre-match ritual, which is a big part of what made San Mamés what it was, was largely unchanged. Licenciado Poza was still packed, still the approach, drawing people to the ground, the same pilgrimage, the same journey, even if it ends at a different destination, the same faces in the same bars, spilling on to the streets. Those same fat guys in the red and white Hawaiian shirts, inevitably sought out by the TV cameras, the same familiar man in his huge Basque txapela, the same red and white shirts, the same cigars, and wine poured from leather "bottles". The same location. Nearly. The same spirit. Nearly.

As fans went into the ground there were queues and rain. Staff in berets showed them to their new seats. Some took wrong turnings – two blokes were sent back from the ladies' toilets – but most agreed that Athletic had got it right. Most agreed, too, that it was very Athletic, that it felt theirs. Right down to the rain. "The spirit is alive," insisted one Basque newspaper. Before the game there was a traditional dance, an aurresku. The 14 captains of the club's various teams together raised the Athletic flag up a mast in the corner and the president laid flowers at the bust of Pichichi, installed here too. The anthem was played, that breathless chant of "Athleeeeeeeetic", voice straining to drag it out as long as possible.

The game was breathless too, a joy. Beñat Exteberría got the first touch, Andoni Iraola the first shot, and Carlos Gurpegui received the first foul at the new San Mamés. The first person to hit the temporary wall with the ball was the Celta striker Charles – and that was from a penalty. He had scored the first goal at the new stadium.

Mikel San José got Athletic's first, the equaliser. And so it went on. There were almost 30 shots, some lovely football and terrible defending, heart-attacks every time Celta threatened and they did often, swift and incisive. But so did Athletic. Back and forth it went. Iraola scored a clever second, set up by Iker Muniain's backheel. Beñat, an early candidate for signing of the season, made it 3-1, finishing superbly. Then Mina made it 3-2. And still there were chances, still the rain came down. But Athletic, who started with 10 players who had come through Lezama, held on. It was, said AS, "a jewel that honoured San Mamés".

Muniain, Beñat and Herrera were withdrawn to colossal ovations. At the full-time whistle, the ovation was for all of them. Not just the players, the whole thing, the whole event, all of them. "Charles will always have a little place in our history," smiled San José, "and so will I."

"That goal was for my grandparents. The stadium is wonderful; it will be amazing when it is finished," said Beñat. "Some of my former team-mates at Celta said it was incredible," added Mikel Rico. "Beyond all the mystique, we wanted to win: we wanted to the team to make the stadium shake with us," said Valverde. "This was an emotional night, a very special one."

"We wanted to be worthy of this stage," the Celta manager Luis Enrique said, describing his team as "privileged" to have been invited to this occasion. He continued: "This is a unique, spectacular stadium. I said that before the game and I can only say that even more so now after it." It was almost one o'clock in the morning and the stadium was quiet now, satisfied. Down on the pitch, grass glistening, Luis Enrique's assistant coach Juan Carlos Unzué, the former Barcelona and Sevilla goalkeeper, was taking photos. A memento. It was raining on San Mamés. The way it's supposed to.

Talking points

• All about Bale? All about Villarreal, more like. The Yellow Submarine were superb against Real Madrid and so was El Madrigal: noisy, yellow and packed. "For much of the game we were the better side," insisted their manager, Marcelino. For pretty much all of it, in fact. Villarreal swarmed all over Madrid, creating chance after chance. It finished 2-2 but it could have been much more, and not just because Villarreal had a penalty turned down in the last minute. Diego López made eight saves and some glorious chances went begging. Villarreal have now won three and drawn one of their opening four. They're back. And brilliantly so.

• If they keep attacking like this and if they keep defending like this, Barcelona are going to be pretty fun to watch. So too are Sevilla, and they might have had more – a goal was disallowed for … well, no one really knows what for. An equaliser in the 89th minute, a winner in the 93rd, set up by a brilliant run from Lionel Messi, who had previously been set up nicely by Neymar, and there might have been more too: the chances just kept on coming.

• Speaking of pretty fun to watch: Betis. Woof! Woof! And woof again! Salva Sevilla, in particular, was class.

• Speaking of pretty fun to watch again: Atlético. Check out the backheel.

• El Hamdaoui scored more in one game than he did in the whole of last season as Málaga walloped Rayo, who have now conceded twelve in three games. And they face Barcelona next. Those Rayo fans who are panicking could do worse than remember last season, mind you.

Results:



Atlético 4-2 Almería

Levante 0-0 Real Sociedad

Barcelona 3-2 Sevilla

Villarreal 2-2 Real Madrid

Granada 0-1 Espanyol

Getafe 2-1 Osasuna

Málaga 5-0 Rayo

Betis 3-1 Valencia

Athletic Bilbao 3-2 Celta de Vigo