Even in a city with La Scala, the glorious opera house, Milan's cathedral unquestionably reigns as the most beloved landmark in Italy's fashion and financial capital.
But the Duomo, as it's known, has also been an extraordinarily high-maintenance icon for six centuries, demanding constant care essentially since construction began in 1386.
The cathedral, along with the 3,400 or so statues and carvings adorning its countless nooks and crannies, and its buttresses and pinnacles and spires, is crafted from rare pink-hued marble mined from a single quarry on the slopes of the Alps, some 96 kilometres to the north.
The stone's unique physical and chemical characteristics make it particularly beautiful. But the stunning colouration also comes with a flaw: The marble is particularly fragile.
"The marble can shatter suddenly," said Francesco Canali, site manager for the Veneranda Fabbrica del Duomo, the association that has been responsible for the restoration and preservation of the monument since 1387.
Veins in the marble contain traces of ferrous materials, and when they, or the iron pins placed through the centuries to link the stones together, oxidise, they expand and shatter the marble into "little pieces or even chunks," Mr Canali explained.
Climate change and pollution are adding to the challenges. "Interaction with the environment has left profound consequences," said Mr Canali, an engineer by training.
The record-breaking heat waves of recent summers mean that the differences in temperature between the parts of the cathedral most exposed to the sun, and those in shadow to the north, can put additional stress on the monument.
Pollutants such as nitric oxide and sulfur dioxide build up black crusts on the marble, "like tartar that preludes cavities in teeth", Mr Canali said.
The cost of all this cleaning and upkeep has always been steep, and now the cathedral, which is "owned by the Milanese", as its archpriest, the Rev Gianantonio Borgonovo, likes to say, has been looking to boost aid from the private sector to cover some of the nonstop expense.
This has led to an "Adopt a Statue" programme, which allows companies to finance the restoration of one of the Duomo's thousands of statues and, in exchange, take it home to show it off for three years.
That's how a striking marble statue of King David holding a harp wound up on proud display in a corporate atrium.
Until the 1960s, the marble statue of the biblical king, carved by an unknown sculptor in the first half of the 16th century, had adorned the Gothic-style Duomo in the centre of the city. But after languishing in a restoration workshop for decades, part of the statue's repair was paid for by a Milan-based adhesives and chemical products company.
"We thought that a Milanese company just had to have a little piece of the Duomo, so it seemed like a wonderful and symbolic project," said Veronica Squinzi, CEO of the company, Mapei.
Officially, the cathedral was finished in 1965, 579 years after it was started, explaining the Italian saying for something that is never-ending: "è come la fabbrica del Duomo", or "like the construction of the Cathedral".
But the continuing need for marble for repair work has been good news for the quarry in Candoglia, a hamlet of 200 people, which has managed to stay operational thanks to its sole customer.
"There's always plenty of work," said Marco Scolari, who oversees the Candoglia quarry and its marble restoration laboratories, of which there are two, one in Candoglia, the other in Milan.
Experts at the Veneranda Fabbrica closely monitor the Duomo's structural well-being, with the entire monument wired with sensors that provide constant digital measurements of varying kinds, "like a constantly working electrocardiogram", Mr Canali said.
Twice a year, too, the cathedral's statuary and decorative elements are given a physical checkup by specialised workers who swing from cranes, inspecting them for fractures and fissures.
When repairs are necessary, the marble is now pre-worked by machines, but specialised training is still necessary for the stone workers called on to replicate the handiwork of long-dead sculptors. "The human hand is essential," Mr Scolari said.
Fabio Belloni, a stone carver at the Milan laboratory, said he had once worked on a single block on the facade of the Duomo for 18 months.
"You have to know the material, where to put your hands, there can be no margin for error," Mr Belloni said. "You need patience," he added, and one wrong move "could betray months of work".
A large part of the decorative stonework on the Duomo dates to the past two centuries, a flurry of activity that followed the completion of the facade -- that Napoleon Bonaparte insisted be done by 1805, so he'd have an appropriate setting for his crowning as king of Italy.
The Milanese of the time didn't embrace that facade, but it didn't stop them from loving their cathedral. The work of the Veneranda Fabbrica was subsidised for years by the donations and legacies of wealthy Milanese, but also by locals of more modest means who would drop valuables in boxes on the construction site that would then be auctioned off.
As recently as a century ago, there was a cafe at the top of the Duomo where Milanese would meet to socialise and gossip.
On the ground, the cathedral's construction workers discovered that the saffron they used to colour stained glass yellow had a savoury side purpose when added to the vats of risotto cooked up for lunch, now known as risotto alla Milanese.
"The Duomo has always been the house of the Milanese," said Fulvio Pravadelli, general director of the Veneranda Fabbrica.
If saints and martyrs have dominated for centuries as favoured subjects, carvers over the years have sneaked in more contemporary figures, including boxer Primo Carnera, a world heavyweight champion in the 1930s, and even a small head of Abraham Lincoln.
Over time, hundreds of statues and decorative motifs have been replaced, the originals ending up in an ersatz cemetery on the city's outskirts.
For the stone carvers in Milan and Candoglia, even the smallest decoration -- which can take months to replicate -- is worth the effort.
"The beauty of our work is to bring forth from a piece of marble something that wasn't there," said Paolo Sabbadini, a stone carver at the Candoglia laboratory, who said that when a piece he was replicating was especially worn, he would add a personal touch to the decoration, even though he knew that at hundreds of feet off the ground, it was unlikely to be noticed, "even with a zoom lens".
"But in theory, we're not working for ourselves," Mr Sabbadini said. "It has to be done well even if you can't see it, otherwise we'd have no reason for being here."
