Chinguetti keeps its libraries in people's front rooms. It is a caravan town on the Adrar plateau of Mauritania, and its manuscripts sit in family houses rather than a museum, looked after by the descendants of the scholars who copied them: hand-inked Arabic on brittle paper, astronomy, law and medicine. To reach the books you cross a dry riverbed that splits the town in two, walking over open sand from the lived-in newer part to the medieval ksar. Herders bring their camels the same way. Over there the lanes climb over drifts and squeeze between half-buried walls to the Friday mosque. Its square minaret has stood since the thirteenth century, split stone laid without mortar and stripped of every ornament. The one exception is at the finials, where you find ostrich eggs set into the stone, read here as a mark of the divine and said to pull lightning off the tower. Non-Muslims see the tower and the courtyard from outside; the prayer hall is closed to them.
The sand is inside that quarter and winning. It pours through doorways, and one house after another has been abandoned to it. Camels take you from the last of them into the erg, where from one crest you see how thin the line between roofs and dunes has worn. The same fight runs tree by tree through the palm grove below the town: some trunks knee-deep, others buried to their fronds, a wall of dune standing behind the green. That grove is what keeps Chinguetti alive, and it gives up a little more ground every year. For six weeks from mid-July the dates ripen and whole families move down into the palms for the guetna, the town's busiest weeks and its worst heat. Then, in a room off a courtyard, a keeper lifts a leather-bound volume out of its chest and opens it across his knee. Some of these have been in the same family for centuries, in a quarter that is being given up house by house.