In the spring of 2008, Doug and Mike Starn began building a wide, arch-shaped structure of lashed-together bamboo poles in a giant disused factory building in Beacon, N.Y. (It remains a work in progress.) At the end of last month, 3,200 similar poles and 30 miles of nylon rope were delivered to the Metropolitan Museum, and the Starns, along with a crew of rock climbers, began constructing a new iteration of Big Bambú. It’s quite a departure from their well-known layered photo works of leaves, trees and other organic material. But last year they completed an ambitious installation in the South Ferry subway station in New York City, so the brothers are not entirely unfamiliar with designing large-scale public artworks.

By the time the rooftop space opens on Apr. 27, the team will have completed a 30-by-50-by-100-foot bamboo scaffold; over the course of the exhibition’s six-month run, the rock climbers will continually fill in this shell so that it forms a dense, undulating wave of interlocking bamboo poles rising 50 feet in the air. Museumgoers will be able to walk around, beneath and even on Big Bambú: adventurous visitors can buy advance tickets on the Met’s website (some will also be available same-day) to ascend the sculpture and experience it from an inside perch.

Photo: Rendering of Big Bambú, a sculpture by Doug and Mike Starn that will take shape on the roof of New York’s Metropolitan Museum over the next six months.