HONG KONG — The Sham Chun River and adjoining wetlands, which separate Hong Kong from the Chinese city of Shenzhen, have throughout modern history served as a physical marker of the differences between the two territories and their distinct systems
However, due to the One Country, Two Systems policy, the two regions maintain a high degree of autonomy, hence they are not governed as part of mainland China. Geologically speaking, Hong Kong and Macau are both connected to mainland China in certain areas , (for instance the north of the New Territories).
Hong Kong and Mainland China are connected by land. Hong Kong is located on the southern coast of China and shares a land border with the Guangdong province of Mainland China. Land, river, and sea depending on the location. The most famous crossing, at Lo Wu, is over a river.