"Stark circle of rock measuring about 60 feet [18 meters] in diameter likes in the Ténéré desert below the massif of Adrar Madet in Niger. Roughly a mile away in each of the four cardinal directions, similarly crafted arrows point away from the circle, whose origin, purpose, and age remain a puzzle."

(Text and photograph from "Journey to the Heart of the Sahara," March 1999, National Geographic magazine)