Grand Canyon National Park is a superstar—biologically, historically, and recreationally. One of the world's best examples of arid-land erosion, the canyon provides a record of three of the four eras of geological time. Almost 2 billion years’ worth of Earth's history is written in the colored layers of rock stacked from the river bottom to the top of the plateau. In addition to its diverse fossil record, the park reveals long-ago traces of human adaptation to an unforgiving environment. It's also home to several major ecosystems, five of the world's seven life zones, three of North America's four desert types, and all kinds of rare, endemic, and protected plant and animal species.