New Arizona Stadium Is Built to Soak Up Sun The Arizona Cardinals open the NFL season this weekend in their brand-new stadium in suburban Phoenix. In a feat of architectural engineering, the facility balances the need to keep fans comfortable in the desert heat -- while still providing real grass for the players. The stadium's roof is retractable, and so is the playing field. On off-days, the entire grass field sits outside the stadium to catch the sunshine. And on game days, it gets rolled inside.