Miller Park in Milwaukee, Wisconsin, home of the Milwaukee Brewers National League baseball team. Completed in 2001, the baseball stadium North America's only (as of 2016) fan-shaped convertible roof, which can open and close in less than 10 minutes. Large panes of glass allow natural grass to grow, augmented with heat lamp structures wheeled out across the field during the off-season. Photo by Carol Highsmith, 2016.