And, yes, nowhere is the city’s widening economic divide clearer to see than along this stretch of Manhattan’s West Side. The new phase loops around Hudson Yards, a 26-acre site becoming a multibillion-dollar architectural petting zoo, with super-tall office and apartment towers, at least one of them to rise higher than the Empire State Building.

But this third phase completes a kind of narrative, which the two earlier phases started, about 21st-century New York as a greener, sleeker metropolis, riven by wealth, with an anxious eye in the rearview mirror. It is a Rorschach test, signifying different things — about urban renewal, industry, gentrification, the environment — to different people. Occupying an in-between sort of space between buildings, neighborhoods, street and sky, the park makes a convenient receptacle for meaning. Neither an authentic ruin nor entirely built from scratch, a sign of runaway capital but also common ground, it is a modern landmark capitalizing on the romance of a bygone New York — the “real,” gritty city — a park born of the very forces that swept that city away.

Image A convenient receptacle for historical meaning: An eastward view of the colossi rising on Manhattan’s West Side, from a strip of the High Line that runs westward along West 30th Street. Credit... Todd Heisler/The New York Times

Those new towers will make this section of the High Line very different from the earlier ones. The first two phases thread, at Hitchcock’s “Rear Window” elevation, through the meatpacking district and Chelsea; it’s the secret garden everybody knows. When Hudson Yards is finished, the development’s raised plaza, built atop the West Side rail depot, will be flush with the 30-foot height of the park, its skyscrapers forming a canyon of glass. The chaos and cranes will be catnip to kids; parents may weep to see another swath of industrial New York yield to luxury condominiums.

James Corner Field Operations designed the High Line with Diller Scofidio & Renfro. Mr. Corner calls the city around the park its “borrowed landscape.” The inimitability of those surroundings, and the park’s site-specific detailing, are major reasons the so-called High Line effect has been, like the Bilbao one, fool’s gold for so many other cities that have wanted to follow in New York’s footsteps.