One time I was assigned to work at a local automotive plant. It was a huge facility, with a lot of open spaces and a metal roof. It was surprisingly comfortable inside the building, though. As I was leaving for the day, I heard a very loud machine and what sounded like a waterfall. I saw one of the largest evaporative coolers I'd ever seen. It was as tall as the building, and massive amounts of water were pouring out of the top. A regular worker told me it was the cheapest way to cool off a building that size.