Monument Valley is located across the border of Utah and Arizona, on the territory of the Navajo Indian Reservation. It is not quite a valley, but rather a flat, arid, eroded part of the Colorado Plateau with huge buttes and mesas jutting out the flatland. The dominant red color is due to iron oxide. The area became world famous after it was used as the spectacular backdrop to several famous Hollywood westerns by John Ford. The two giant rock formations in the picture are called East Mitten and West Mitten; their enormous size can be recognized if one compares them to the car in the bottom right corner.