A Prehistoric Solar Observatory in the Middle of Sahara Desert

The prehistoric stone funerary monuments of the Sahara desert, distributed in a huge geographical area, had been created in several different shapes. Some of them have a design that looks like a keyhole, and therefore are known as keyhole tombs. Since they are facing the sunrise, these tombs had been proposed as places for the worship of the sun too. In this paper, we show that one of them, in Algeria, has two radial lines oriented with the sunrise azimuths of winter and summer solstices. This monument is then a prehistoric solar observatory in the middle of Sahara.