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.
... out with 20.6% under the age of 18, 5.0% from 18 to 24, 26.8% from 25 to 44, 27.7% from 45 to 64, and 19.9% who are 65 years of age or older. The median age is 43 years. ...