Video: Metrodome Roof Collapse
The Hubert H. Humphrey Metrodome opened in 1982. Its signature feature is its Teflon-coated fiberglass fabric roof that is literally inflated by the air inside the stadium. The stadium is pumped full of air to keep the roof up. This requires people to enter and exit the dome via airlocks, to maintain positive pressure within the playing field area.
Over the weekend, the roof collapsed under a heavy load of snow -- and the dramatic collapse was caught on video (see below). But this is the fifth time a "deflation event" has happened. Wikipedia explains the other four:
Five times in the stadium's history, heavy snows or other weather conditions have damaged the roof and caused it to deflate. On November 19, 1981, a rapid accumulation of over a foot of snow caused the roof to collapse, requiring it to be re-inflated. It deflated the following winter on December 30, 1982, again because of a tear caused by heavy snow. This was four days before the Vikings played the Dallas Cowboys in the last regular season game of the 1982 NFL season. In the spring following that same winter, on April 14, 1983, the Metrodome roof deflated because of a tear caused by a late-season heavy snow, and the scheduled Twins' game with the California Angels was postponed. On April 26, 1986, the Metrodome roof suffered a slight tear because of high winds, causing a nine-minute delay in the bottom of the seventh inning vs. the Angels.
And here's the fifth:
The Boston Globe has before and after photos.