Nanjing:

Located in Yangtze River Delta area and the center of East China, Nanjing is home to one of the world's largest inland ports. Nanjing is also one of the fifteen sub-provincial cities in the People's Republic of China's administrative structure, enjoying jurisdictional and economic autonomy only slightly less than that of a province. Nanjing has been ranked seventh in the evaluation of "Cities with Strongest Comprehensive Strength" issued by the National Statistics Bureau, and second in the evaluation of cities with most sustainable development potential in the Yangtze River Delta. It has also been awarded the title of 2008 Habitat Scroll of Honour of China, Special UN Habitat Scroll of Honour Award and National Civilized City. Nanjing boasts many high-quality universities and research institutes, with the number of universities listed in 100 National Key Universities ranking third, including Nanjing University. The ratio of college students to total population ranks No.1 among large cities nationwide. Nanjing is one of the three Chinese top research centres according to Nature Index.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What does Nanjing have that is considered one of the world's biggest?
inland ports