Běi-Shàng-Guǎng-Shēn shì Zhōngguó de yīxiàn chéngshì.
Beijing, Shanghai, Guangzhou and Shenzhen are China's first-tier cities.
Tips
usage
Each character stands for one city: 北 Beijing, 上 Shanghai, 广 Guangzhou and 深 Shenzhen. Leave Shenzhen out and you get the older 北上广. Both are used for the big cities as a type, with their jobs, high rents and long hours.