The span of Rainbow Bridge was reported in 1974 by the Bureau of Reclamation to be 275 feet (84 m), but a laser measurement in 2007 has resulted in a span of 234 feet (71 m). At the top it is 42 feet (13 m) thick and 33 feet (10 m) wide. The bridge, which is of cultural importance to a number of area Native American tribes, has been designated a Traditional Cultural Property by the National Park Service.
Two other natural arches, Kolob Arch and Landscape Arch, both also in southern Utah, have confirmed spans several meters longer than Rainbow Bridge, but by most definitions of the terms they are considered to be arches rather than bridges. With a height of 290 feet (88 m) Rainbow Bridge does indeed stand taller than either of its longer competitors, but it is outdone by Aloba Arch in Chad at 394 feet (120 m).
The world's tallest (though less easily accessible) arch is Töshük Tagh, better known as Shipton's Arch, in China at an estimated 1,200 feet (370 m). Finally, Xianren Bridge (also known as Fairy Bridge), in Guangxi Province, China, with a span of about 295 feet (90 m), and a height of the opening of 210 feet (64 m), appears to be the natural bridge with the largest span in the world.
According to wikipedia
