Justo Gallego is sitting in a backroom of the cathedral he has been building for the last half century. Dressed in a blue boiler suit, he is perched on a chair and under a red woolly hat, his 89-year-old face lean and tanned.

“I’ve had lots of ideas,” he says, excitedly explaining where he found the sources of his inspiration. “For example, I had the idea of making a small version of the Vatican’s dome. I also got ideas from medieval castles – I’ve mixed medieval castles with the Romanesque style.”

All these influences and more can be seen in the enormous, unfinished building which he began in 1962. Its seemingly endless domes, arches and spires sit on the edge of Mejorada del Campo, a small town 20km east of Madrid. Built out of recycled materials and junk, it is a divinely inspired work of imagination for some – and an eyesore for others.

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Tuberculosis

Gallego joined a monastery at the age of 27, but was forced to end his career as a monk just a few years later when he contracted tuberculosis.

“I left the monastery, came back here and started making something big for the Lord.” He says he still considers himself a monk.

“I’ve never been with women because I’m celibate, as ordered by God, as if I were in a monastery. For me the church is my wife.”

The money from an inheritance funded the cathedral project, but Gallego, who had worked as a labourer before taking his vows, had no training as an architect. Unfazed, he sketched the design in dust on the floor and now donations from visitors help finance its construction.

Now in his 90th year, Gallego delegates most of the more physically demanding work to a volunteer, Ángel López, who lives in the cathedral with him.

Gallego is so absorbed in his work that he has little contact with the people of Mejorada del Campo, who, he says, have never understood his vision.

“When I first came out of the monastery, they said ‘he’s crazy, he’s crazy’,” he recalls. “That’s what they think and they still don’t see what I’ve done here. But I have to respect them, I don’t hold it against them and I even pray for them.”

But Eduardo Pérez (33), a local who describes the cathedral as “a miracle”, says attitudes have changed.

“Twenty years ago, a lot of people criticised him, saying ‘he’s just crazy, he’s wasting his time’,” he says, as he admires the cathedral from across the road. “But nowadays, since the cathedral has got this big, people come from around the world to see it. People from the town are just beginning to realise it’s something valuable and wonderful that we should admire and take care of.”

Despite its unconventional design, the scaffolding surrounding it and the interior's resemblance to a building site, in many ways Gallego's opus resembles other Catholic landmarks across Spain. It has stained glass windows, a sacristy and a crypt and storks have nested on top of several of its towers.

Eccentric temple

Given that it remains a work in progress, it is impossible not to be reminded of Barcelona's still uncompleted Sagrada Família, another eccentric temple designed by a devout Catholic with a vision, Antoni Gaudí.

Gallego can see the comparison, but he’s not convinced.

"Gaudí­ was surrounded by the rich folk of Catalonia, I've seen a picture of him with people wearing elegant hats and drinking wine," he says. "But that's not like me – I'm on my own."

With plenty of work still to be done on his cathedral, it’s difficult not to wonder if, like Gaudí, Gallego will die without seeing his masterpiece completed. Ángel estimates that money, rather than time, is the problem, with a further €100,000 needed to finish it. Gallego himself is ambivalent.

“It would be very vain of me to finish it, because then people would praise me and I don’t want praise,” he says. “But of course, I’d like to finish it, it is important to me. Then I’d hide and that would be the end of it.”

Gallego spends much of the day wandering around his extraordinary creation, giving instructions to Ángel and contemplating the building’s eventual completion.

“People are lost,” he says. “Their feelings are based around material things and because that doesn’t make them happy, they look for something else: bullfighting or soccer, or they go travelling, off to India – and that’s not right. You can’t just decide ‘I’m going on holiday to India’. Only when God allows you to. You have to ask His permission to go there.

“But nobody does that, because they don’t have faith. They don’t believe. What do people believe in? They believe in this idea that’s all about moving around and vanity – and more and more vanity.”