The imperial city of Chang'an during the Han Dynasty was in northwest of today's Xi'an. During the Tang Dynasty, the area to be known as Chang'an included the area inside the Ming Xi'an fortification, plus some small areas to its east and west, and a major part of its southern suburbs. The Tang Chang'an was 8 times the size of the Ming Xi'an. During this time Chang'an was one of the largest and most populous cities in the world. Around 750 A.D. Chang'an was called a "million people's city" in Chinese records, while modern estimates put it at around 800,000–1,000,000 within city walls.