THE ARTIST Christo and his late wife/collaborator Jeanne-Claude have used fabric to spectacular effect. They wrapped Germany’s Reichstag in polypropylene, “hung” a curtain across a Colorado Valley, and, in 2016, built a floating, three-kilometer-long walkway across a lake in northern Italy for a work called The Floating Piers.

The installation lasted just 16 days, and was intended to have a maximum daily capacity of 45,000 people.

By the second day though, nearly 20,000 people an hour had poured onto the pier. Even after organizers instituted aggressive crowd control by closing down the nearby train station and restricting bus access, the final visitor tally, when the 16 days were over, was more than 1.2 million people. For context, that’s about a fifth of the annual attendance of the Vatican Museums.

In the new documentary Walking on Water, directed by Andrey Paounov, viewers are treated to a behind-the-scenes look at how the project unfolded — and how Christo has gamed the art market to serve his own ends.

As a record of the floating piers themselves, the documentary is invaluable. From planning meetings with local bureaucrats to the construction of the piers themselves (they were made up of 220,000 high-density plastic cubes that fit together like puzzle pieces, which in turn were wrapped with 100,000 square meters of dazzling, orange-gold nylon), the project evolves from an abstraction into a cultural phenomenon.

As the crowds literally sprint towards the piers on the opening day, the power and draw of participatory artworks is brought home with astonishing force. “We [are on track to have] 200,000 people in one day,” one of the organizers says, panicking. “If it was half that amount — 100,000 people would be too much. It’s madness.”

Later, the same man is less sanguine: “Who f*cked up and told us the maximum we’ll ever have is 45,000 people?” he asks, wild eyed as crowds surge their way through the town.

By the time the project was realized, Jeanne-Claude had been dead for seven years, and Christo, then in his mid 80s, was in charge of organizing it on his own. But even though he’s at the center of it all, the documentary doesn’t provide insight into why he wanted to build a floating walkway in the first place.

The closet viewers get is at a kick-off talk to the builders in charge of assembling the project. “It’s a project Jeanne-Claude and myself tried to do — where you can walk on water,” he says. “All of the money from the project comes from me, the works of art I do by my own hand. We have no assistant. I sell the works, and it pays the bills.” (The only real glimpse of Christo’s “process,” if you could call it that, is a series of excruciating clips where he bickers with subordinates.)

In one of the more fascinating scenes in the whole documentary, a collector in a suit and tie gets out of a gorgeous wooden motor boat and is led by a team — presumably all representatives of Christo — into a building on the shore of the lake, where he’s shown a series of Christo’s artworks that depict the Floating Piers.

It becomes apparent that the collector was promised one price for a large work — $250,000 — but that in the interim, the price has changed. “Christo produced 40 original works,” a representative explains with a half-hearted stab at contrition. “Very few are available, they are gone each day, [and each day the prices] go up.”

The same representative gestures to a large drawing on the wall. “A week ago, this was 1.6, today it’s 2.2,” he says, shrugging, meaning $2.2 million. “I mean, what can we do?”

Finally, the collector settles on a mid-sized work, which costs $500,000. “I have a CEO, which is my wife,” he says. “And luckily she has good taste for contemporary art.”

It’s rare that you can see the sausage getting made so explicitly, but in the film, Christo is unapologetic about using his collectable art to fund his transient installations. It’s also clear which version of his practice he actually cares about.

At a fancy cocktail party to celebrate the Piers opening, women in shimmering dresses and men in summer suits take turns getting lightly insulted as Christo makes his way through the crowd. “Do you remember me?” asks a woman brightly, her face falling into a frozen half-smile when Christo says he doesn’t. “In Rome I gave a dinner for you” she tells him. “Yes, yes, now I remember,” he says vaguely and moves on.

A man drops the names of his parents in law. “Galen Weston?” he says, naming one of the richest men in Canada. Christo nods: “Yes of course, big collectors of ours,” he replies, as if that’s a compliment in itself.

And in a way, it is. Christo might be a diva on occasion, but he’s managed to convince a few very wealthy people to effectively underwrite large-scale projects that cater to millions. Moreover, his continued ability to capture the imagination of all strata of society is a testament to the potency and potential of contemporary art.

After all, the Piers, he reminds people, aren’t just an attraction — they’re an artistic experience. “I’m flattered that so many people have come,” he says in a press conference announcing new crowd-control measures. “But if you’re in a hurry, don’t come.” — Bloomberg