How are cities in cities formed, and how many places in China have cities in cities.

Kaifeng is a famous cultural city with a long history. Kaifeng, located in the hinterland of the Central Plains and on the bank of the Yellow River, is one of the main birthplaces of the Chinese nation with a history of more than 2,700 years. During the Spring and Autumn Period, Zheng Zhuanggong built a granary city here and named it "Kaifeng", which means "opening up the frontier". Later, it was renamed Kaifeng after avoiding the taboo of Emperor Liu Qizhi of the Han Dynasty. Wei in the Warring States period, Hou Liang, Houjin, Houhan and Houzhou in the Five Dynasties, the Northern Song Dynasty and the Jin Dynasty all established their capitals here, which is called the "Seven Dynasties Metropolis". Especially in the Northern Song Dynasty, from the mutiny in Chen Qiao to the partial security in the Southern Song Dynasty, after nine emperors 168, it was the political, economic and cultural center of the whole country at that time, and was also an international metropolis, with the reputation of "Wufeng Tower in the Ming Dynasty, the imperial capital of Yimen since ancient times" and "Bianjing is rich in the world". The Riverside Scene at Qingming Festival by Zhang Zeduan, a painter in the Northern Song Dynasty, and Dream of China in Tokyo by Meng Yuanlao vividly depict the bustling scene of Kaifeng, an ancient capital. During this period, Bao Gong, Yang Jiajiang, Yue Fei, a national hero and Wang Anshi, who are determined to reform, emerged in Kaifeng, which had a great influence on the development of China's history.