History: Mali Empire: Its most famous ruler, Mansa Musa, is often considered the wealthiest person in history, once causing a gold inflation crisis in Egypt during his pilgrimage.
History: Byzantine Empire: Although they called themselves Romans, the official language of the empire was eventually changed from Latin to Greek.
History: Persian Empire: The Achaemenid Empire was the first to implement a professional postal system, known as the Chapar Khaneh, using a relay of horses.