Culture : Florentines Await Unveiling of Skyline’s Domed Jewel : After 15 years of work and controversy, 4,000 square meters of 16th-Century frescoes will be back on display.

A long and expensive courtship between art and science has finally paid off for Florence, bringing peace at last to one of the world’s favorite skylines.

The giant eight-sided cathedral dome that is Florence’s civic signature is emerging from a 15-year, $7-million structural checkup and artistic overhaul with a fresh face and a clean bill of health.

That should delight visitors, and it may even mollify critics who have long insisted that restoring mediocre art was not worth the risk of damaging a dome that is a priceless architectural marvel.

A soaring, mesh-shrouded scaffold that has obscured the interior of the dome since 1980 will be removed in June to reveal 4,000 square meters of restored 16th-Century frescoes.

Spotted among them is a network of sophisticated monitoring instruments designed to safeguard the future of the 15th-Century dome whose construction by Filippo Brunelleschi wrote a bold new chapter in the history of architecture.

Controversy that has so long raged around the dome of Santa Maria del Fiore cathedral is symptomatic of the difficult decisions conservationists must make--and the passions they inevitably arouse--in a country whose artistic legacy is unsurpassed.

Meanwhile, the good news that the 500-year-old cathedral dome will continue to grace Florence has been matched this winter by word from Pisa that another illustrious monument is on the mend. Reacting to 600 tons of lead ingots stacked around the raised north side of its foundation, Pisa’s 800-year-old tower has stopped leaning. The weights have actually eased the tower one centimeter back toward the perpendicular.

The work goes on in Pisa, but here respite awaits the dome that Florentines have scrutinized with affection and alarm ever since it was finished.

“When the scaffolding comes down, we fully intend that it should stay down for many generations,” said architect Riccardo Dalla Negra, an arts ministry official who has overseen the work inside the cathedral.

The cupola was controversial even before it was built. When Brunelleschi won a civic competition in 1418, many Florentines said it would be impossible to cover the vast vaulted altar area of the church without extensive buttressing--construction of support pillars to prevent the dome from collapsing under its own weight.

Brunelleschi built it without supports nonetheless, borrowing herringbone techniques of brick-and-stone-beam construction from the ancient Romans. Hardly had the completed red brick dome been consecrated in 1436, though, when it began to develop cracks--some of them big enough to stick an arm through.

How to preserve the dome instantly became a civic preoccupation in Florence. Amid growing cracks and unsuccessful attempts to stanch them, it has remained high on the municipal agenda--subject of endless learned debate--for more than 500 years.

Furthermore, the decoration chosen to illuminate the interior of the dome, a gigantic fresco of the “Last Judgment,” has been the subject of timeless and disputatious discussion among the habitues of Florentine coffee bars for generations.

Giorgio Vasari began the work in 1572, but it was finished by Federigo Zuccaro. Vasari was a prolific decorator but a so-so painter. His greatest contribution to the Renaissance was as a biographer and an architect: He designed the Uffizi Gallery, another Florence landmark, and in 1550 published “Lives of the Artists,” biographical profiles of geniuses like Michelangelo and Leonardo da Vinci that college students still read today.

As a painter, Vasari was a mannerist. His work on the cupola, begun near the top, is a static exercise of precise formality. Zuccaro took over after Vasari’s death in 1574. He was a younger man and an artist of a very different stripe, a precursor of the Baroque era that would dominate Italian art following the Renaissance. His work has an almost impressionistic aura. Seen from up close on the platform, some of it looks almost freestyle in contrast to the careful figures of Vasari.

The bottom line: The sum of the vast painting may be impressive as it sprawls across the vast domed surface, but it is more a document of its times than great art.

“There is of course no way we can compare this ‘Last Judgment’ to Michelangelo’s in the Sistine Chapel,” says Cristina Danti of the National Arts Ministry, who helped oversee the restoration of the painting. (After 14 years of restoration of its own, the Sistine Chapel “Last Judgment,” by the way, makes its own return to public viewing after Easter.)

“The Sistine Chapel was commissioned by a Pope. This is a work commissioned by civil rulers--the Medici,” Danti observed. “It is an important document of Renaissance art and history. It is not to traditional, classical Florentine tastes. There are even portraits of the painter, his family, the master builders and their crew.”

Important, perhaps, but hardly a favorite among the people of a city that houses some of the world’s best art. Hard to see at the best of times from the cathedral floor, nearly the length of a football field below, the painting became darkened and obscured by centuries of candle smoke. Even as the costly scaffolding went up in 1980, Florentine critics--in some cases echoing their great-grandfathers--argued that the cheapest and most merciful restoration for the inside of the dome would have been spackle under a coat of whitewash.

“That was proposed in the 19th Century, and even today there are people who ask why we’ve bothered to restore this painting. But it has a certain strength. I like it,” said Danti as she walked along the upper reaches of the narrow, dangling scaffold.

Whatever the merits of the frescoes, their restoration has allowed architects and engineers to undertake a painstaking study of the dome itself, inventing along the way a series of highly sophisticated instruments to monitor stress on the dome.

A vocal minority of Florentine notables, including architect Lando Bartoli, 81, warned of dire consequences when erection of the current scaffold began in the late ‘80s. They particularly objected to the filling with cement of 48 Brunelleschi-designed holes that held the Renaissance scaffold and also the new one.

The openings, Bartoli insists, are essential “breathing holes” for a dome that expands and contracts with heat and cold. He believes that even temporary closure must aggravate the cracks and weaken the dome over the long haul.

The holes will be reopened this summer as the scaffold comes down. But the high-tech instruments arrayed around the cupola circumference will remain as an investment in the future.

Despite critics’ concerns, their readings so far have been reassuring, according to project director Dalla Negra. Florence’s marvelous cupola is aging quite gracefully, thank you.

“What we’ve found in fact is that the dome is healthier than we thought it was,” says Dalla Negra.