It is one of the canyons of the world and stands on both sides of the Colorado River. It is on the northwest side of Arizona, bordering Nevada. It is about 446 km long and about 29 km wide. The average depth of this wonder is about one mile (1.8 km). According to geologists, the flow of the Colorado River over millions of years formed it. It is the fourth-largest canyon in the world in size and volume. But it is the most famous wonder in the world, with about 6.2 million tourists walking every year.