Listener Steve Karsch wrote to tell us about the Desert Libraries of Chinguetti. From kottke.org:

For hundreds of years, families in Mauritania have been maintaining libraries of old Arabo-Berber books. Originally on the route of pilgrims travelling to Mecca, the libraries are now at risk from the spreading Sahara and ever dwindling numbers of visitors, in part because of security restrictions due to terrorism.

Check out this thread from @incunabula to learn more.