Mercedes Benz Stadium, Atlanta

The 2-million square foot, 71,000-seat Mercedes Benz Stadium is styled after the Roman Pantheon, as the entire arena is centered around a domed oculus. Because the building is multi-use – designed for holding football, soccer, and basketball games – and because Falcons owner Arthur Blank had wanted to build what he described as an “iconic stadium” with a retractable roof, a watertight aperture was designed for the roof.

Comprising eight 200-foot-long, 450-ton blades clad in Ethylene Tetrafluoroethylene (EFTE) film, the roof’s semi-transparent iris is capable of opening and closing in only nine minutes. Because every petal needs to swing into place at a different speed, not rotate like a true aperture, the roof uses an algorithm to judge how much counter-balance is needed while the blades are cantilevering out over the field. Reinforcing the centralized focus of the design is a 350-ton, six-story, ring-shaped “Halo Board” seated inside the oculus itself that’s viewable from every seat and angle.

Outside, the stadium’s base is a wall-to-ceiling glass curtain wall meant to give uninterrupted views of the surrounding city as fans make their way to their seats. Eight steel and glass “leaves” radiate out from the aperture at the top of the stadium and drape down over the glass at the bottom, referencing the swooping wings in the Falcons’ logo. Work on the roof is still ongoing, and engineers hope to have the aperture fully functional by the time Atlanta hosts the Final Four basketball tournament in 2020.