The Grand Canyon is certainly the most famous canyon in the world and arguably the most beautiful and grand indeed. The canyon is 277 miles (446 km) long and as deep as 6,000 feet (1800 m). The Colorado River has been carving the canyon for 5-6 million years, exposing nearly two billion years of geological history. Technically part of the Colorado Plateau, I've given the Grand Canyon its own gallery here due to its unique character and immense geographic area.