The otherworldly rock formations in the Bisti/De-Na-Zin Wilderness inspired some creative names—such as the "Alien Egg Hatchery" seen in this photo. More than 70 million years ago, this desert was a tidal swamp along the shore of the long-evaporated Western Interior Seaway that once bisected North America. A diverse array of sediment and rock was deposited by the waters, and after the seaway retreated, the rocks remained.