The Museum of Modern Art collects and prizes the sculpture and designs of Isamu Noguchi, a towering figure in 20th-century American art. But just across West 53rd Street, the developer of 666 Fifth Avenue, Brookfield Properties, is planning the opposite: dismantling one of Noguchi’s largest sculptural installations, one that he called “a landscape of clouds” that he designed in 1957 in the skyscraper’s twin lobbies.

On either side of a central bank of elevators, the Japanese-American sculptor, who pioneered the idea of sculpture opening into, and shaping, the environment, designed an upside-down ocean of backlit, undulating aluminum blades floating in a light of its own making. The entire space glows. Just outside the lobbies in a passage connecting West 53rd to West 52nd Street, a former water wall of vertical blades stands, an upright version of the ceiling. Until several years ago, before the water was turned off, it acted as a cascade, water rippling over a washboard of corrugated glass and falling into a bed of plants, creating an acoustic oasis in Midtown.

This wall and the ceiling in the lobbies are intact, but they are not landmarked. Brookfield Properties, which now has a 99-year lease on the building, intends to remodel the lobbies as part of a building-wide renovation, disassembling and perhaps donating the pieces to an outside group, if one presents itself.

The developers say Noguchi’s work, because of changes in a previous renovation, no longer has any integrity meriting preservation. “It in no way reflects Noguchi’s original vision,” Andrew Brent, a spokesman for Brookfield, wrote in an email.