Charles Long: Pet Sounds, Madison Square Park, New York; Tomás Saraceno on the Roof: Cloud City, Metropolitan Museum of Art, New York

It’s a fantastic moment for outdoor art in Manhattan. Psychedelic blobs are disgorging strange noises in Madison Square Park, and a multi-faceted agglomeration of mirrored pods has sprung from the roof of the Metropolitan Museum. Both projects practically command the public to get physical with them. At the Met, visitors can clamber over Tomás Saraceno’s “Cloud City,” a floating space station that seems to have landed briefly to refuel. With “Pet Sounds,” Charles Long invites the public to prod, tap and massage his bulbous fibreglass beasties. Each stroke generates a quasi-musical retort: a low whine, a minimalist bleating, or a wa-wa blast.

Long’s anamorphic shapes are fastened to leash-like tubes that whir and thrum as they wind through the green acreage, mimicking the maze-like patterns of the park’s pathways where people wander with their actual, flesh-and-fur animals. “I hope I might be an interloper into the park visitors’ unconscious, into what Freud has called the free-floating attention,” Long has said. “I like the idea of ‘Pet Sounds’ becoming a part of the collective memory, and even dreams, of the unique experiences of New York City.” That’s how the best public art works, not by sticking out, but by binding with the cityscape and becoming at once comforting and strange.

On a warm spring afternoon in Madison Square Park, it’s a bubble-gum creature, sprawled across a picnic table, that enchants kids the most. They’re not at all repelled by its freshly chewed-and-spat-out look, or by the way it seems slick with saliva. They rest their ears on its puckered surface and latch their arms on to its swollen pink folds. Nearby, a bald man in a plaid shirt has parked himself next to a purple walrus-like thing. Every few minutes he lays a tentative hand on its tiny “head,” as if to check that it’s still breathing. A few steps away from this tender pair, a huge grey form strikes a pose that’s part-elephant, part-centrefold, balancing its mushrooming bulges on a delicate base. Groups of adults come up to fondle it, running their palms along its fatness and leaning in to hear what it has to say. People mingling with the “pets” become integral parts of the sculpture, bringing them to life with their groping hands.

Long taps into a vein of surrealism running from Man Ray to Dalí to Louise Bourgeois, but without mainlining their sadism. His jellybean-coloured organisms, cute and vaguely obscene, straddle representation and abstraction. They are adult objects that bring out the kid in everyone.

Saraceno, too, mines the plastic fantasies of childhood, when the line between the biological and inanimate worlds seems more permeable. His walk-through installation on the roof of the Met has the feel of a toy that’s started to grow. It could almost have been built out of Lego, except that instead of snapping together bunches of identical rectangular blocks, he has piled up polygonal modules made of steel and acrylic. The capsules all look the same at first, but examine them more closely and they begin to differentiate: they tilt, bulge, or stretch; some panes are mirrored, others transparent. The resulting structure looks at once futuristic and prehistoric, techno-wonky and animate. Like an enlarged photo of some microscopic fractal phenomenon, “Cloud City” reminds us that crystal structures exist at every scale. From a distance it could be the head of foam on a well-poured pint of lager. Approach, and the human creatures climbing through the pods resemble bees in a giant honeycomb.

To have the full experience, visitors must obtain timed tickets, shed bags and cameras, and be wearing rubber-soled shoes – no heels, and skirts aren’t ideal either, given the multiple levels and see-through floors. Thus freed, you scramble up some stairs and through a labyrinth of reflective surfaces, ducking beneath low frames and stepping gingerly on platforms that could be mirrors disguised as windows, or the other way around. Look down and you see yourself, reflected and askew. Step into the next chamber, still looking at the floor, and beneath your feet a panorama of green trees and blue skies sparkles up through the fractured planes. Saraceno wants you dizzy and wowed, the better to trick you into defying gravity and falling upwards into the clouds. The piece weighs 20 tons, yet it looks as if it would float away if not for an invisible tether.

Saraceno and Long approach outdoor art from different aesthetic perspectives; Long’s work has a homemade look, while Saraceno’s is tough and industrial. But both artists have figured out how to woo audiences distracted by their chaotic urban habitat. This is harder than it seems. Sculpture in the city often looms, preens, or blares for attention, or else it squats, unnoticed and unloved, vanishing into the saturated topography. But these two installations have hit a sweet spot, where art and urbanism speak to each other, and the crowds become physically enmeshed in that juncture. You shouldn’t – and most of the time, you can’t – see the works in solitude, because they draw on the vitality of those who stop and play. In this case, art is other people.

‘Charles Long: Pet Sounds’ continues until Sept 9, ‘Tomás Saraceno on the Roof: Cloud City’ continues until November 4 (weather permitting),

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