worldhistoryfacts:

worldhistoryfacts:

Kyz Kala, a 7th-century CE fortress outside of the city of Merv (in modern day Turkmenistan). Although now off the beaten path, Merv was a central trade city along the Silk Roads because it was near a key oasis in the dry central Asian environment. By the twelfth century, it was one of the largest cities in the world, containing perhaps 200,000 people. When the Mongols arrived in the 1220s, they supposedly slaughtered almost the entire population of the city, and Merv never regained its prominence.