Khizanat al-Qarawiyyin, in the old medina of Fez, Morocco, is reopening after a four-year restoration. Founded in the ninth century, the library’s prized collection—which includes a ninth-century Koran written on camel skin in ornate Kufic script—is kept safe behind a wrought-iron door with four locks. The restoration began shortly before Islamic State and other jihadists became increasingly threatening to Islamic-heritage sites in Syria, Iraq and Mali. But restorers had to deal with a more immediate problem: the heat and humidity of the Moroccan climate. Leading the project is Aziza Chaouni, a Fez-born architect who has installed a new underground-canal system to draw moisture away from the texts, and a temperature- and humidity-controlled room to house the most precious works. From this month, scholars are being allowed back into the library; it will be formally opened to the public once more with a visit from the king next year.