Rush is a relative term when talking about a building under construction for the past 125 years.

But the pace of carving and hoisting has clearly picked up at the Sagrada Familia church in Barcelona, Antoni Gaudí's unfinished masterpiece and one of Spain's top tourist sites.

The church's 250 craftsmen have been hurrying to get the central nave finished in time for the visit next weekend by Pope Benedict XVI, who will consecrate the church as a Basilica, more than a century after Gaudí's first parabolic line was drawn in stone.

"I've been working intensely by day and recently, because of the visit, at night," said Japanese sculptor Etsuro Sotoo, who created 30 giant pieces of fruit and Eucharist symbols, each 4m high and weighing 15 tonness, for the 60m-high roof.

So when the Pope offers his blessing next Sunday, he will find a minor miracle: this seemingly endless construction project is nearly complete. Well, that's another relative term. The stained glass windows are still missing, and so are many of the interior sculptures. A handful of spires have yet to be erected, and the final Facade of Glory is still a blank slate.

But the 6,500 invited guests, including 1,000 priests and 100 bishops from around the world, will pray amid a forest of columns, inclined like growing trees. Overhead, the faithful will see vaults covered in brick and green-and-gold tiles, fractured in Gaudí's characteristic mosaic style, trencadis. They will listen to a 2,000-pipe organ.

"From an architectural point of view, it's finished," said Armand Puig, author of a recently published book, The Sagrada Familia According to Gaudí.

Following the consecration, daily mass will be held at the Sagrada Familia, whose full name is the Expiatory Church of the Holy Family. Until now, services were held in a basement chapel.

For Jordi Bonet, the Sagrada Familia's 85-year-old chief architect, the consecration is the crowning moment of 44 years of work. "I never thought we would go this far," he says. "I thought maybe we would be able to cover the nave but not the whole church." He is especially relieved to see the tourist attraction open for continuous worship. "This is a church, not a theme park," he said. "Gaudí conceived of it as a tribute to the Lord."

The undulating church is expected to be fully, and finally, finished by 2025, but as Mr Bonet points out, "Gaudí always said, 'My client isn't in a hurry.'"

If it ever happens – and some people hope it does not because they think the place is much more interesting with scaffolding – it will have 18 spindly spires for tourists to gawk at and an esplanade for an unobstructed view. Last year, 2.4 million visitors paid the €12 entrance fee to snap pictures of the Tree of Life on the Nativity Facade or climb the stairs to see the mosaic-covered ceramic balls.

But since its inception in 1882, the Sagrada Familia has attracted almost as much controversy as tourism. Many 19th century observers ridiculed Gaudí's work, which transcended the canons of modernism with those dream-like organic forms.

His style was too much even for surrealist painter Salvador Dali, who called the building "a tactile erogenous zone" and praising Gaudí's "superbly creative bad taste".

At the start of the Spanish Civil War in 1936, anti-clerical anarchists set fire to church, burning Gaudís workshop and his sole plaster model. It took 10 years to reconstruct.

"It could have been worse, the anarchists wanted to blow up the Nativity Facade, but someone convinced them that the heavy falling stone would crush them if they did," says Mr Puig.

George Orwell wished the anarchists had gone all the way. He considered the Sagrada Familia one of the most hideous buildings in world.

Work resumed in the Fifties as Spain shook off post-war poverty, but many artists opposed the posthumous construction, which is paid for by private donations and entry fees. "They felt it offended his memory," said Jose Maria Giralt, an engineer who leads a club of 25,000 Gaudí aficionados.

In 1990, another generation of Spanish artists and intellectuals took aim at the stark Facade of the Passion created by sculptor Josep Maria Subirachs. They even published a book that poked fun at his style. "This sculptural mess is the logical consequence of the architectonic mess made by the false continuers of Gaudí," wrote prominent Barcelona architect Oriol Bohigas.

Less high-brow criticism, according to Mr Giralt, centred on Subirachs' decision to include the genitals on a sculpture of Christ.

Even some Barcelona locals are weary of the growing monument. "It's a source of pride, but in reality, it is causing more and more problems, between the tourist traffic, fast food shops and delinquency it's driving the residents away," said Manel Ruiz of the Sagrada Familia neighbourhood association.

Most recently, Gaudí's project faced a threat from an unlikely source: the Public Works Ministry, which decided to dig a tunnel for a high-speed train several metres away from the building's foundations. The Sagrada Familia board of directors lobbied for years to reroute the tunnel and even won symbolic backing by international architects and the Spanish parliament, but workers ploughed on anyway – with precautions – in early October. The building survived.

"Just because nothing happened now doesn't mean the danger is over," said Pere Vallejo, head of the citizens' platform against the tunnel. "In 10 years, when the ground settles, then we'll see."

But concern about tunnel has been overshadowed lately by the upcoming consecration, eagerly awaited by the architect's ardent admirers, including many people who want him to be declared a saint.

"This is a dream come true," said Jose Manuel Almuzara, president of the Association Pro Beatification of Gaudí. "Gaudí's dream was that, through this church, generations of people would give glory to God."

The architect's case has been under consideration by Vatican experts in such matters since 2003. Mr Almuzara said Gaudí deserves the honour not for his architecture, which he believes is capable of "bringing people closer to God," but because of his "exemplary life".

Jose Maria Tarragona, a founder of the pro-sainthood movement, even considers Gaudí a mystic on the order of Saint Francis of Asisi or Saint John of the Cross. "But his vision wasn't just poetic, it was scientific," Mr Tarragona said.

Gaudí's colourful mosaics and organic curves burst with a sensuality absent from his austere, hum-drum life. He was often sick as a child. He is known to have had only one brief romance. He lived with his parents until the last 10 years of his life, when he moved into his workshop at the Sagrada Familia. Nuns served him a vegetarian supper. His passion: long nature walks.

He was extremely pious and so fond of fasting that at age 42, he nearly died during Lent, according to Mr Tarragona.

And when money to build the Sagrada Familia was tight, he pleaded for alms to continue.

"He renounced his fee and every afternoon he went out on the street to beg – imagine Picasso or the Beatles doing that," said Mr Tarragona.

In 1926, he was hit by a car as he walked to mass, pockets empty, wearing his usual tattered attire. Taxis refused to take him to the hospital because they thought he was a beggar. He died in a pauper's hospital three days later. "My place is among the poor," he reportedly told his friends.

So what would the monk-like Gaudí think about the morphed state of his unfinished work today?

He would approve of it, according to Mr Puig, even with its mixture of styles. "Gaudí didn't work for it to remain half-finished," he said. He even said, 'I am not going to be the one to finish it. It will be finished by the ones who succeed me.'"

Etsuro Sotoo is part of the line of succession. When he came to Europe in 1978, he wasn't interested in Gaudí or the Sagrada Familia – "I just wanted a rock to chisel," he said – but after 32 years of sculpting angles and fruit he has become intimately acquainted with the Catalan creator. He even converted to Catholicism. Rather than copy Gaudí, he tries to think the way Gaudí did.