The Black Mailbox is a wonderfully odd roadside stop on the Extraterrestrial Highway between Alamo and Rachel. Its fame comes from Area 51 folklore: visitors leave notes, stickers, and alien-themed offerings at a lonely mailbox in the desert, turning a practical object into a small pilgrimage site for UFO road-trippers.
There is very little here beyond the mailbox, the emptiness, and the story, which is exactly the point. Bring water, fuel up before the drive, and treat it as a quick stop in a long desert landscape rather than a destination with facilities.