In New York City these days, residential towers cannot be too slim or too tall. The improbably slender form of One57, now fully enclosed, is the furthest along of a new crop of super-thin, supertall, super-luxe residential towers. Designed by Atelier Christian de Portzamparc for Extell Development Company, with glass panels of blue, pewter, and silver, it rises 1,004 feet, hundreds higher than even its tallest neighbors.

Just blocks away, CIM Group and Macklowe Properties' 432 Park Avenue will top out at even greater height, 1,396 feet. The square floor plan, extruded without setbacks in concrete with punched windows, has reached about 45 stories. It is as proportionally pristine as a Sol LeWitt sculpture—an image of “pure strength,” says its architect, Rafael Viñoly. Nearby, SHoP Architects is still refining its design for the 1,350-foot-tall building planned for 111 West 57th Street. So far, it is the slimmest of about a dozen super-skinny, supertall towers planned or under construction in New York. The ultrathin buildings are intended to lure buyers willing to plunk down as much as $95 million for a home perched high in the sky.