The Grand Canyon is a place that should be experienced by everybody in order to appreciate just how insignificant we are compared to the natural forces and time that combined to form this wonder of the world. According to Wikipedia, nearly two billion years of Earth's history have been exposed by the Colorado River's erosive efforts. That's 'billion' people, 'BILLION!'.
There's more to explore up near the border around Page and Lake Powell. The similarities with neighbouring Utah are very evident here with more crazy rock formations and sandstone everywhere. A great state!