Al-Ma'mun at the first degree measurment.(German: Der Kalif Mamun veranstaltet die erste Gradmessung).Caliph Al-Ma'mun/Almamon/ Al-Maymun/ el-Mâmoûn- Abbasid caliph (813-833).Liebig card, Episodes from the Caliphate, 1897. (Photo by Culture Club/Getty Images) *** Local Caption ***
