Tourists walk down part of the Great Wall of China. In addition to the oceans and manmade borders that surround the country, China's geography and the harsh terrain on its borders have often served to isolate the country from its neighbors.
Contemporary China is an island. Although it is not surrounded by water (which borders only its eastern flank), China is bordered by terrain that is difficult to traverse in virtually any direction. There are some areas that can be traversed, but to understand China we must begin by visualizing the mountains, jungles and wastelands that enclose it. This outer shell both contains and protects China. Internally, China must be divided into two parts: the Chinese heartland and the non-Chinese buffer regions surrounding it. There is a line in China called the 15-inch isohyet, east of which more than 15 inches of rain fall each year and west of which the annual rainfall is less. The vast majority of Chinese live east and south of this line, in the region known as Han China — the Chinese heartland.
