Horsetail Fall is seasonal waterfall which flows in winter and early spring. The fall comes off the El Capitan mountain in two distinct streams and drops some 1570 feet onto steep slabs spraying up in a mist before continuing down another 500 feet to the bottom of the mountain.
But as beautiful as the fall is by itself, it is the few days every year during the last two weeks of February when it becomes the "fire fall" that people wait for. As the sun sets, and dips behind the horizon line, everything will begin to go dark and it will seem, for a moment, as if the firefall has failed to ignite. But as the last of the sunlight disappears it will hit and reflect off the falls at the exact right angle creating a spectacular, if short lived, effect which looks like a beautiful flowing cascade of fluid fire.
Bizarrely, Yosemite Park used to actually create "fire falls" by pushing huge piles of coals off the edge of a cliff. These were an incredibly popular tourist sight from the 1880s all the way through the 1960s when the park realized this was a fire hazard (which seems kind of obvious) and stopped. Luckily this natural phenomenon was able to pick up where the park rangers left off.