The Chinese Military Headquarters is the Chinese's main building of operations in Shanghai. It contains many classified info hidden within the Chinese army until the Russia and Confederation decided to capture it.
In Power Hunger, it's the main target of the "mind-controlled" Russians and Confederation, and must be captured by an Engineer during the later half of the mission. It is completely invulnerable, so the player will not have to worry of accidentally destroying it.
Back in 3.0 and 2.0, the Military Headquarters had a different model. It was elliptical and was much larger compared to its current model.