Under Islam, Cordoba may have been Europe’s largest city. Istanbul, conquered in 1453, became the seat of the Orthodox patriarch and chief rabbi as well as of the caliph. Shah Abbas’s new capital, Isfahan, had 29 churches and an Armenian cathedral.

 After the arrival of paper in the eighth century, they opened madrassas, or academies, with vast libraries. Qarawiyin, founded by a woman in 859 in the north African city of Fez, is the world’s oldest continually surviving academic institution.

The third Mughal emperor, Akbar, launched a new universal creed, complete with an interfaith think-tank, the Ibadat Khana.