Please answer a question about the following article about Nanjing:

Nanjing is an important railway hub in eastern China. It serves as rail junction for the Beijing-Shanghai (Jinghu) (which is itself composed of the old Jinpu and Huning Railways), Nanjing–Tongling Railway (Ningtong), Nanjing–Qidong (Ningqi), and the Nanjing-Xian (Ningxi) which encompasses the Hefei–Nanjing Railway. Nanjing is connected to the national high-speed railway network by Beijing–Shanghai High-Speed Railway and Shanghai–Wuhan–Chengdu Passenger Dedicated Line, with several more high-speed rail lines under construction.

Nanjing's railway is important, and is located in what region of China?
eastern China