An interesting article describing the construction of the very innovative Arizona Cardinal stadium complete with retractable roof and roll-out stadium floor with natural turn playing surface which is rolled inside only on game days, the rest of the time the turf is outside soaking up sun.
From the article… The stadium’s nominal seating capacity of 63,500 for the Cardinals’ National Football League (NFL) games is expandable up to 73,000 to host marquee games, such as the annual Tostitos Fiesta Bowls, the BCS Championship Bowl (in January, 2007) and the NFL’s Super Bowl XLII (in February, 2008)
See article here on Amerisurv or seeHigh resolution PDF Article Available here