The U.S. Tennis Association unveiled its retractable roof over the main court at the USTA Billie Jean King National Tennis Center in Queens on Aug. 2. It cost $150 million and took more than two years to install. Moving at a speed up to 25 feet per minute, the roof over the 23,771-capacity stadium is built to close or open in under seven minutes. The 62,500 square-foot opening in the roof could fit 22 tennis courts.