The Chinese phrase Four Great Ancient Capitals of China (中国四大古都 pinyin zhong1 guo2 si4 da4 gu3 du1) refers to Nanjing, Beijing, Xi'an, and Luoyang.
... aware of this. It remained a problem in geography until the invention of chronometers at the end of the 18th century A.D. It mus be added that his original topographic ...