The Grand Canyon is nearly 446 km (300 miles) long, 29 km (18 miles) wide, and over 1,8 km (1 mile) deep. To the best of my knowledge, there is no other canyon of comparable size in the world.
Is this in fact the case? If no, which canyons are larger? If yes, what made the Grand Canyon so much larger than others? What is, perhaps, a "fusion" of several other, smaller canyons linked by the Colorado River? Were the rock formations surrounding the Grand Canyon in some ways more "continuous" than others in the world? Were there at one time other canyons of comparable size elsewhere in the world that somehow got broken up into smaller entities?