Great Divide

In the northeastern region of the Earth Kingdom lies the Great Divide -- the largest canyon in the world. "Experts" say that the canyon was probably formed by earth spirits who were angry at the local farmers for not offering a proper sacrifice. .... There is no shrubbery or water inside the canyon, and bringing food is dangerous because it attracts Canyon Crawlers - giant ant-like creatures that could -and would- easily swallow you whole.

Apparently, it is necessary to cross this canyon in order to reach the capital city of Ba Sing Se, and takes about a day or two to cross on foot. Many of the paths leading into and out of canyon are sheer cliffs or have giant gaping holes preventing further travel. Luckily, the Great Divide Tour Guide is an Earthbender, so he can easily create stone paths and bridges long enough for those with good intentions who need to cross.