The Yosemite Firefall was a summer time ritual that lasted from 1872 until 1968 in which burning hot embers were dropped a height of about 3000 feet from the top of Glacier Point in Yosemite National Park down to the valley below... The ritual ended when the hotel burned down in 1969. The hotel was never rebuilt, and park rangers decided to disallow continuing the ritual due to the overwhelming number of visitors it attracted, and the fact that it was not a natural event.Modern "firefalls" are created when waterfalls are illuminated by a setting sun. The best explanation I've seen is at Shutterbug.
Via Reddit. Photo credit to Jeff Sullivan at Panoramio.