Ibn Khordadbeh

Ibn Khordadbeh was a ninth-century official of Persian descent; his grandfather was a Zoroastrian who converted to Islam. He served as director of the caliphal postal and intelligence service in the province of Jibal and later in Samarra and Baghdad, and became a companion of caliphs, known also for his knowledge of music.

His Book of Roads and Kingdoms (Kitab al-Masalik wa'l-Mamalik), first compiled around 846 and revised around 885, is the earliest surviving Arabic work of administrative geography. It lists postal routes, staging posts and distances across the caliphate and beyond, with notes on trade routes, peoples and lands as far as China, Korea and Japan.

It is also the first source for the journey of Sallam the Interpreter, sent by Caliph al-Wathiq to find the barrier built by Dhul-Qarnayn against Gog and Magog. According to the Encyclopaedia Iranica, Ibn Khordadbeh heard the account from Sallam himself, and later geographers repeated it.