Largest retractable stadium roof

The world's largest retractable roof covers the SkyDome, home of the Toronto Blue Jays baseball team, near the CN Tower in Toronto, Canada. Completed in June 1989,  the roof covers 3.2 ha (8 acres), spans 209 m (685 ft) at its widest point and rises to 86 m (282 ft). It weighs 11,000 tonnes (24.6 million lb), equivalent to 6,000 cars, and takes 20 minutes to open fully. When retracted, the entire field and 91% of the seats are uncovered. The roof consists of four sections: the first is stationary and all the other parts are stored underneath it when the roof is open. The second and third parts simply 'telescope' back under it, whilst the last section rotates 180º before moving into place. The stadium itself has a capacity of 67,000 for concerts, 55,000 for Canadian football and 50,600 for baseball.