The youngest city in China
As China is a country with 5000 years history, many Chinese cities also have thousands years history. However Shenzhen, a city with 7 million polulation, has only 20 years history. It was a village with a few fisherman until 1979 when China starts its open door policy. In less than 30 years, Shenzhen has been transferred to a modern city with all the skyscrapers and highways.
Due to lack of history, there is no any historic sightsees in Shenzhen. However, I think Shenzhen has the best theme parks in the country. There are different kinds theme parks such as "Window of the World", "Chinese Folk Culture Village", "Happy Valley" etc. Shenzhen is also a shopping paradise. There are lots of large department stores and small shops, you should definitely visit Dong Men walking street. Shenzhen also has best IT products shopping centers in Hua Qiang North.