Sol LeWitt’s sculptures have sprouted in City Hall Park like spectacular hybrids of architecture and vegetation, blooming between bench and fountain, flowering among the bins, and winding lazily among bustling crowds. These huge creations gossip lightly with the trees and delve into more serious tête-à-têtes with the neighbourhood’s skyscrapers. “Sol LeWitt: Structures, 1965-2007” is the first outdoor survey of his most monumental works, with 27 pieces from every stage of his career sprinkled like candy across this small patch of Lower Manhattan greenery. Organised for the Public Art Fund by its director and chief curator, Nicholas Baume, this stellar array of outdoor sculpture makes the most of loans from across the globe. City Hall Park seems at first like an unpromisingly congested site for such still, whispering work, but it turns out to be an ideal summer showcase. Here, anyone with the time to pause between meetings can trace the whole paradoxical arc of a career that was at once remarkably consistent and riven by leaps of startling variety. The vast, sleek white cubes, the orderly arrangements of polyhedrons, and finally the rococo “splodges” with their twisting, melting globs of colour are all sensuous odes to logic and structure. Yet the order in which they are seen here depends entirely upon which entrance a visitor happens to take on their way to lunch. Those coming from the north will encounter the cubes first, while the slouching rainbow tower, “Splotch 15”, accosts people arriving from the south. LeWitt, who died in 2007, always balanced the organic and built environments, finding architectonic elements in nature and bringing forth the fluidity and grace buried in geometry. He found a way to join apparently incompatible extremes – intellect with emotion, rigour with spontaneity, flinty severity with expansive lyricism. So it’s fitting that here, pristine white cubes from LeWitt’s early career seem to rebut the picturesque sway of trees, reasserting the city’s grid of streets and echoing the abrupt angles of surrounding buildings. And the later work, complex, irregular and even baroque, dovetails with Frank Gehry’s rippling new skyscraper at 8 Spruce Street. In the contemplative cocoon of the museum, LeWitt’s oeuvre comes across as a series of abstract, self-contained procedures, flowing from his rule-making mind and assembled by a team of fabricators. In the mid-1960s he wrote: “When an artist uses a conceptual form of art, it means that all the planning and decisions are made beforehand and the execution is a perfunctory affair. The idea becomes the machine that makes the art.” That pristine, self-contained logic falls by the wayside in City Hall Park, a perpetually crazed nexus of traffic, pedestrians, architecture and greenery. Here, his art connects with the chaotic world, with a fabric of existence outside his head and removed from his obsessive need for control. The current installation reveals him to be a profoundly urban artist who recapitulated virtually the whole history of New York architecture, visible within steps of the spot where his sculptures now sprawl. LeWitt’s early cubes resonate with One Centre Street, a premodernist building that, in its formal neoclassicism, echoes their austere pattern of vertical and horizontal bands. Those cubes’ architectonic construction also mimics the ubiquitous steel-cage framework that first permitted early skyscrapers to rise at the turn of the 20th century, and still forms the skeletons of buildings as they climb out of their foundations and take their place on the Manhattan skyline. The white stainless steel of LeWitt’s modular building-blocks harmonises, too, with the sleek enamelled skin of the Woolworth tower, which shoots toward the sky from another end of the park. In later years, as he moved away from orthogonals and used computers to build more irrational shapes, LeWitt’s interests paralleled those of architects who relied on new technologies to produce the sinuous facades or faceted surfaces of the 21st century. For “Complex Forms 6” (1987), LeWitt drafted a two-dimensional polygon and placed dots at various points within it. As he projected the form into three dimensions, those interior loci rose into space at different heights, creating multifarious, crooked shapes that converse excitedly with Gehry’s tower just across the way. LeWitt’s work deals with rhythm and variations in density, with volumes that huddle and expand, lines that inch near each other before they veer apart. Here, on this pitch of grass in the hub of grey Manhattan, those thrumming variations pick up on the city’s ever- shifting rhythms. Amid the thick stream of office workers pouring into the park at lunchtime, or the thinning traffic as dusk settles, these organic oscillations express an inner aesthetic core of LeWittian logic. Perhaps it’s just an artefact of Baume’s expert placement, but the dialogue between sculpture and building illuminates new aspects of both. The stacked windows and faceted planes of the architecture, crisply shadowed and outlined in the summer sun, look suddenly more sculptural. And LeWitt’s seemingly inert boxes come to life as urban microcosms, embryonic cities of their own. “Sol LeWitt: Structures, 1965-2007” continues until December 2.