These days the Icelandic artist Olafur Eliasson, who lives in Copenhagen but works out of Berlin, is thinking of the impact of water cascading by the ton. Not quite five years ago, however, and quite by chance, he found out how charged with meaning one raindrop can be. The epiphany occurred at the time of "The Weather Project," which consisted of an artificial sun enshrouded in mist, blazing for six months in the cavernous Turbine Hall of the Tate Modern in London. Having consented to produce a tie-in for the gift shop, Mr. Eliasson went up to the roof one rainy day, collected some precipitation in a plastic bag and had single droplets encapsulated in cubes of Plexiglas. The cubes went on sale the day the installation opened and sold out before closing time. Mr. Eliasson never authorized a second edition.
Weeks later, however, he received a postcard from a woman who had recently lost her husband. "She had happened to visit the museum on opening day and had bought one," he says. "It had a label with the date when I collected the raindrops, which turned out to be the same day that her husband had died. In her mind, it was a teardrop."
For Mr. Eliasson, the fact that the widow had invested the object with personal significance nearly redeemed what he had come to think of as a somewhat tacky bit of merchandising, but not enough to have another go at this sort of thing. At 41, he prefers to pursue his agenda of "generosity" and "intimacy" -- two favorite terms -- by means of public art. The New York City Waterfalls, his grandest project yet, consists of four man-made cataracts sited on the waterfront in Brooklyn, Lower Manhattan and Governors Island. In height they range from 90 to 120 feet, in width from 30 to 80 feet, each scaled to and aligned with its surroundings.
"In essence, the hardware consists of a scaffold with a trough on top," Mr. Eliasson says. "The trough is filled with water pumped up from the base. If you can fill the trough, which the engineers know they can, all you have to do is keep pumping, and the water overflows. There's not much to test."
Two years in the planning, under construction since March 17 of this year, the falls are scheduled to run from tomorrow through Monday, Oct. 13, 7 a.m. to 10 p.m. daily (except Tuesdays and Thursdays, when the starting time is pushed to 9 a.m.) As Mr. Eliasson sees it, the work of art here is the experience: the approach, the contemplation, the going away. "Expectation. Engagement. Memory," Mr. Eliasson says. "You can't take a journey with you." The only souvenirs will be ones you carry in your head.
"If the doors of perception were cleansed," William Blake once wrote, "everything would appear to man as it is, infinite" -- infinitely personal, Mr. Eliasson might add, and infinitely interconnected. His business, above all, is the cleansing of the doors of perception. Visitors to his current show "Take Your Time" (continuing at the Museum of Modern Art and P.S. 1 Contemporary Art Center through June 30) are discovering immersive environments and sensory-deprivation devices of unfathomable beauty: a rotunda flooded in constantly shifting colors, a gigantic tilted mirror slowly rotating overhead, a cubic meter traced by lamplight in vapor in a darkened gallery. What sense can be made of these Zen mysteries? What do they mean?
In his clinical, uncluttered designs, Mr. Eliasson walks the walk of an experimental physicist; in the thorny Teutonic abstractions he often uses to explain his thinking, he talks the talk of a student of phenomenology. Is he either? "Occasionally one, occasionally the other," Mr. Eliasson replies. "Relevance arises through context. Sometimes you are looking at pure forms, sometimes at an argument."
Likewise, he is a psychologist. "Say you go home to visit your mother," he suggests, "and she didn't make the pie she always makes but a different pie. Should you complain, or should you be glad that she took a stand, changing with time? You expect to travel back to your childhood. You don't want things to change. You want security, predictable patterns. But is it fair to burden your mother with that? Isn't it more inspiring if she's part of life and not static, part of the past?" Whimsically, Mr. Eliasson gives places the same inner life as people: "Should New York be the old pie or a new pie? Maybe I want the Village to look like it did in the '80s, when Avenue C was a mess, but Avenue C wants to be fancy now. It wants to be contemporary."
He is exquisitely attuned to nuances of sound and light, which he also recalls with Proustian accuracy. Strolling down by the waterfront, he finds beauty in a mound of road salt deposited under the Manhattan Bridge like sooty slush out of season. Pointing to the sky, he conjures up the trajectory of the sun and gathering darkness in terms that merge drama and epic.
Political theory, ecology and ethics likewise enter the picture. "People like to think that public space is neutral and open to all. Actually, it is subject to commercial interests, to the intentions of power elites. Public space is what's left when everything else has been privatized. We need to create it, we need to nurture it. I didn't dump down the waterfalls from the moon. I tried to integrate them with the city in a productive way."
Digital renderings give a vivid impression of what to expect but, as Mr. Eliasson keeps saying, a waterfall is not a picture. It makes noise. It cools the air. It gives off spray. "It almost doesn't make sense to talk about the waterfalls now," he said. "It's like talking about a painting that hasn't been painted yet. I can't wait to see it."
Locals have been getting previews. According to a chance eyewitness at the northernmost waterfall, by Pier 35 in Manhattan, a test run there brought traffic on the East River Drive to a dead halt. Gawkers by the hundreds materialized from adjacent Chinatown within minutes. And what did it look like? "I'll show you," the eyewitness said, whipping out an iPhone. At the touch of an index finger, waters came crashing down against a stormy sky at the rate of better than 8,000 gallons per minute: a video Niagara on a 3.5-inch screen.
"It's so loud! I can't think," Mr. Eliasson said on that same spot one blistering June afternoon, grimacing at the roar from the highway overhead. The pumps were idling then. "But I think that when people see the water falling, they'll absorb the traffic noise into the sound of the water. Close your eyes! Doesn't that sound like a waterfall?"