At a total height of over a thousand metres (3,212 feet), and the longest single drop of 2,648 feet, Kerepakupai-merú (Angel Falls) in the forests of southeastern Venezuela is the highest waterfall in the world, 15 times higher than Niagara falls. The water rolls off the top of Auyan Tepuy, a mesa or table mountain made of sandstone. There are over a hundred of these mesas all over the Guiana Highlands in Venezuela, each of them with almost perfectly vertical sides and a flat top, being gradually eroded by the trickle (or, in this case, the flood) of water down their sides. The falls are on the Carrao river, a tributary of the Caroni, which eventually joins the Orinoco, which itself joins the Amazon on its way to the sea.
It is named after Jimmy Angel, the pilot who 'discovered' it by accident in 1933 while flying through the mesa's Devil's Canyon looking for gold. He returned in 1937, landing his monoplane in a bog near the top of the falls and descending the cliffs with his companions to hike for 11 days back to civilization. His plane remained on top of the mesa for 33 years, until it was lifted out in 1970 and turned into a tourist attraction at an aviation museum. A replica was created and left at the top of the falls in memory of Jimmy, one of the most famous adventurers of his time. Actually, the falls had been first documented in 1910 by Ernesto Sanchez la Cruz, a Spanish explorer; and of course, the local Venezuelans had known about the falls for centuries, but they don't write the history books.
Angel Falls is now an extremely popular location for base jumping, in which thrill-seekers are flown to the top of the mesa so that they can fling themselves off, opening their parachutes at some point on the way down. It also attracts a great number of more conventional tourists who just want to witness one of the Natural Wonders of the World. There are no roads, and the only way to reach the falls is by plane like good ol' Jimmy, or by the more conventional bushwhacking route through the rain forest.
http://www.kented.org.uk/ngfl/rivers/River%20Articles/angelfalls.htm
http://www.bootsnall.com/cgi-bin/gt/samericatravelguides/sep99angel.shtml
http://www.ladatco.com/ANGL-ABT.htm
http://www.extremescience.com/Hfallspage.htm