In Lower Manhattan, just east of the World Trade Center site, nine subway lines converge, linked by a web of dark underground passageways. The network of tunnels, near Fulton Street and Broadway, has never been described as welcoming. But that’s about to change, with the completion of a transportation and retail hub known as the Fulton Center. The most visible part of the center, designed by Grimshaw Architects under the supervision of Arup, is a new building containing curved stairways down to the subway platforms. A skylight was always part of the building’s design. But how could it be made to ­deliver the maximum amount of light to the below-ground portions of the station?

For this design problem, James Carpenter, an artist and designer, devised a 25-metre-tall installation. It consists of 952 diamond-shaped aluminium panels suspended from a net of steel cables in a ­hyperbolic-paraboloid hourglass formation. This is no mere artwork, but a huge, architecturally scaled and technically precise creation: by reflecting light onto subterranean surfaces, it becomes a beacon and locating device.

As the design of the Fulton Center changed, ­Carpenter’s installation had to change with it. Initially, a glass dome was to top the building. With a redesign of the building, the dome be-came an opaque truncated cone containing offices and mechanical spaces. In cooperation with the engineers, Carpenter and project designer Richard Kress created a lightweight net of steel cables stretched between the upper and lower steel rings. (Fred A. Bernstein)