Throughout most of its history, Istanbul has ranked among the largest cities in the world. By 500 CE, Constantinople had somewhere between 400,000 and 500,000 people, edging out its predecessor, Rome, for world's largest city. Constantinople jostled with other major historical cities, such as Baghdad, Chang'an, Kaifeng and Merv for the position of world's most populous city until the 12th century. It never returned to being the world's largest, but remained Europe's largest city from 1500 to 1750, when it was surpassed by London.