In the searing heat of the desert, a sculptured pool of stainless-steel shimmers as it reflects the bright sunlight, the image constantly changing with the time of day and angle at which it is viewed. It stands as an artistic representation of a mirage—or at least it stood. Because this work of art, like a mirage and the shifting sands of the desert, is transient, and now that the art exhibition has closed, it leaves behind no trace. It was one of the monumental installations of Desert X AlUla, a temporary art exhibition staged on a spectacular scale in the striking sandstone landscape of Saudi Arabia’s AlUla oasis.