Art: It's the chapel of his eye

Sol LeWitt, Sixties minimalist, has an odd new painting job in Italy. Matthew Sweet met him

Sol LeWitt is the gran-daddy of American conceptual art. So pure is his commitment to the superiority of idea over object that, in 1987, he sold an intangible concept at auction - for the very concrete sum of $26,400. Ownership of the work was indicated by a typed certificate, which specified that it should be executed in black pencil and consist of "10,000 lines about 10 inches long, covering the wall evenly". The owner, the Manhattan art dealer David McKee, has the right to reproduce this piece as many times as he likes. If you were to try it at home, you'd only have a fake on your living room wall - despite the fact that LeWitt would not have picked up his brush in either case.

Sol LeWitt's work has been at the vanguard of US art since the 1960s, and encompasses creations formed from Styrofoam wall panels, modular steel units and highly-coloured fibreglass ziggurats. Given this pedigree, the septuagenarian Modernist's current project seems rather quaint. It's the restoration of a turn-of-the-century chapel in a vineyard in north-west Italy.

The building is situated a few miles from the town of Alba, in the region of Piedmont. It's an area famed for its wines, but Alba itself is dominated by the Dantean sprawl of the Ferrero Rocher plant, the largest chocolate factory in the world. Which is great if you're an ambassador who wants to spoil his guests with a pyramid of soft centres, but not so great if you've got a sweet tooth for culture. If it's art you're after, you'd best get on the bus to Milan.

A year ago, however, Bruno Ceretto, the head of a successful family of wine-producers, decided to do something about the region's cultural poverty. The Cerettos are in the Barolo business, and their vineyards ramble over land which is reputedly the most costly real estate on the planet. Thanks to a deal with the French champagne house Veuve Cliquot, their wines are now also gaining a foothold in the the lucrative US market. They're not short of a lire or two.

While on holiday on the Cote d'Azur, Bruno Ceretto visited the Chapel du Rosart in Vence, a building which Henri Matisse designed and decorated between 1948 and 1951. It struck him that a dilapidated chapel in one of his vineyards - then being used as a makeshift garage - might be turned over to a similar project. He approached LeWitt and the British artist David Tremlett to turn the chapel from a ruin to a piece of contemporary art, and they readily accepted - perhaps because Ceretto offered to pay their fee in bottles from the family cellars. Tremlett elected to oversee the redecoration of the interior, LeWitt the exterior. "If we'd tried to share the space any other way we wouldn't be speaking by now," LeWitt admits.

Bruno Ceretto is not an art patron in the model of Vivian Duffield or Charles Saatchi. He's an unpretentious man with a rather earthy turn of phrase (which his daughter and chief translator, Roberta, effortlessly transposes into perfect Euro PR-speak). "I can't judge their work as an art critic," he confesses. "Before all this started I preferred a round of golf to going to a gallery. And I can't understand why they've chosen to do it in the way that they have. But when I went up to the chapel with Sol, I could see in his face that he knew exactly what to do. We just sat there, looking at the landscape. It was like being in paradise." He's so pleased with his first foray into Medici territory that he plans to offer a whole series of buildings on his estate to the brushes of contemporary artists. "We produce wine from the soil of this land. Now we're going to give something back to it."

Even during its garage incarnation, the chapel was never deconsecrated by the Catholic Church, and therefore remains an official place of worship. Once work is completed at the end of this month, the local priest will be yomping up the hillside for a grand opening ceremony, after which it will be used as a venue for the occasional service. As he worked on the designs, however, LeWitt tried to dissociate the space from the burden of its history and its religious function. "I didn't see it as a church or a chapel, not even as a building, but as a thing to be used to make a work of art," he explains. "I thought of it as an abstract form. It would not be so much a Catholic church, more a place where people could go inside and meditate, be enclosed with colour and light and form." For him, the chapel is an installation, as strikingly out of context with its surroundings as he has been able to make it. David Tremlett had similar instincts, but as it fell to him to design a chasuble for the priest, he was not free to exercise the same degree of detachment. In contrast to LeWitt's instinct for brash, bold hues (the chapel's exterior is a bright burst of paint in a landscape of peach and terracotta-coloured soil), Tremlett works in pastel earth-tones, applying them with the palms of his hands for a softer, smudgier effect. The surplice is covered in circular blotches of colour, and as he rolls out his actual-size design on a long table in the winery, I'm struck by its resemblance to a Twister mat. However, as Tremlett is in the middle of telling me how the landscape of Piedmont reminds him strongly of the hill-country of Eritrea, I keep this observation to myself.

"I'm nomadic," he explains, from under his raffishly battered fedora, as we look over the chapel's cool interior. "I've always travelled to obscure parts of the world and remained there for long periods of time to work. I'm a scavenger, and Sol is a mathemat- ician, but strangely enough we come to many of the same aesthetic conclusions."

For LeWitt, working for an old Italian family makes a refreshing change from the faceless corporations - Swiss banks, auction houses, multinational companies - for which he and his team of assistants have completed many of their recent commissions. "The Medici tradition has been carried on by the individual art patron in Italy, and that ideal is still very much alive - mainly because there are very few public galleries of contemporary art." However, there's a limit to the extent he's prepared to romanticise such notions: "My function is to make art - unless the corporation or the personality who's given the commission is so manifestly evil that I couldn't go near it with a stick. But corporations as such are okay. It's like artists painting for the church in previous centuries. It's just a way of doing work." And unlike his $26,400 concept-for-hire, this particular piece of work - strong, bold, and visible across the Piedmonte hills for miles around - will perhaps be the most tangible of his long career.