Having failed sadly in its emulation of Rockefeller Center, the plaza opposite the Plaza will now try being more like the Louvre.

By fall, a glass cube 32 by 32 by 32 feet will be set like a jumbo gemstone into the middle of the plaza of the General Motors Building at 767 Fifth Avenue. From the outside, the cube will appear empty. But inside will be a circular glass stairway and a cylindrical elevator leading to a 25,000-square-foot underground space.

In other words, the cube will function like I.M. Pei's Pyramid in the Cour Napoléon of the Louvre: a crystalline marker, a gateway into a subterranean realm. Only the local version will be more transparent -- even the structural framework is to be made of glass -- and, this being New York in the year 2005, it will usher visitors not to culture but to retail, almost certainly a much larger version of the Apple Computer store in SoHo.

The plaza itself will be relandscaped. The slightly elevated bosque at the south end, reached by wraparound steps, has already disappeared behind construction barriers. Its twin on the north end is also destined for demolition. The new plaza will be on a single level from 58th to 59th Streets, framed at each corner by low, wide, L-shaped parapets.