AP Explains: Retractable roof and moveable field make Super Bowl stadium stand out

With its retractable roof and moveable field, University of Phoenix Stadium is unlike any stadium anywhere.

Its unique design allows games to be played inside in the air conditioning when it's hot out or have an outdoors feel when the roof is open. The moveable field makes it possible to grow the natural-grass field outside in the sunlight and move back inside for games.

A quick rundown of University of Phoenix Stadium, site of Sunday's Super Bowl between the Seattle Seahawks and New England Patriots:



University of Phoenix Stadium opened in 2006 after three years of construction to serve as the home of the NFL's Arizona Cardinals, which had played at Arizona State's Sun Devil Stadium after relocating from St. Louis in 1988. It also has been the site of the Fiesta Bowl every year since 2007 and hosted the 2008 Super Bowl.

Designed by architect Peter Eisenman, the $455 million stadium is the first in North America to have a retractable roof and a moveable field. Though designed to resemble a barrel cactus, it is more often said to look like an alien spaceship because of its silver, disk-like shape.

The stadium a capacity of 63,400 and can expand to 72,200.



University of Phoenix Stadium is one of four in the NFL with a retractable roof, along with Houston, Dallas and Indianapolis.

The roof has two retractable panels that weigh about 550 tons each and cover the entire field when closed, allowing the stadium to be air conditioned when it's hot outside. The panels are made of translucent fiberglass that allows natural light in and the roof, which sits 206 feet above ground level, is supported by two 700-foot trusses.

The roof takes about 15 minutes to open or close, but most games are played with it closed. Since 2006, the Arizona Cardinals have played with it open 22 times in 93 games.



The Cardinals wanted to have a wanted to have a natural-grass field in their new stadium, but the design of the retractable roof would not allow enough sunlight in to properly grow the grass.

To accommodate the grass, stadium designers made it so the entire field could be moved in and out of the stadium on a series of wheels, gears and rails. Moveable fields had been built for professional soccer teams at the GelreDome in Arnhem, Netherlands and the Veltins-Arena in Gelsenkirchen, Germany, but this was the first time it had been done in North America.

The tray holding the field measures 234 feet wide and 403 feet long, and weighs more than 18 million pounds. It's wheeled in and out of the stadium on 546 steel wheels that ride along 13 parallel steel rails, traveling 741 feet in about 75 minutes.

The grass, a Bermuda hybrid, was grown for a more than year at an Alabama farm, then was cut into sections that were rolled up and transported in 33 refrigerated tractor-trailers.


AP NFL website: www.pro32.ap.org and www.twitter.com/AP_NFL