The Grand Canyon is a steep-sided canyon carved by the Colorado River in northern Arizona. It is one of the Seven Natural Wonders of the World and is a UNESCO World Heritage Site known for its layered geological history that is exposed due to the long erosion of the Colorado River. Stretching for over 277 river miles, the canyon and adjacent rim are contained within Grand Canyon National Park, the 15th site designated as a UNESCO World Heritage Site by the United States.