Merv

Merv (Marw), in present-day Turkmenistan in the historic region of Khurasan, was one of the largest cities of the medieval Islamic world and a major centre of learning, briefly the residence of the Abbasid caliph al-Ma'mun. The hadith compiler Abu Dawud al-Sijistani (d. 889) and the traditionist al-Darimi (d. 869) are connected to its district; the geographer Yaqut al-Hamawi worked in its libraries.