China is situated in eastern Asia, bounded by the Pacific in the east. The third largest country in the world, next to Canada and Russia, it has an area of 9.6 million square kilometers, or one-fifteenth of the world's landmass. It begins from the confluence of the Heilong and Wusuli Rivers in the east to the Pamirs west of Wuqia County in Xinjiang Uygur Autonomous Region in the west, with about 5,200 kilometers apart. In the north, it starts from the midstream of the Heilong River north of Mohe and stretches south to the southernmost island Zengmu'ansha in the South China Sea, with about 5,500 kilometers in between. The Chinese border stretches over 22,000 kilometers on land and its coastline extends well over 18,000 kilometers, washed by the waters of the Bohai Sea, the Huanghai, the East China and the South China Seas. The Bohai Sea is China’s only inland sea. There are 6,536 islands larger than 500 square meters, the largest being Taiwan, with a total area of about 36,000 square kilometers, and the second, Hainan. The South China Sea Islands are the southernmost island group of China. China, one of the four oldest civilizations in the world, has a written history of 4,000 years and boasts rich cultural relics and historical sites. It is the inventor of compass, paper, gunpowder and printing. The Great Wall, the Grand Canal and the Karez irrigation systems are three great ancient engineering projects built 2,000 years ago. Now they are the symbols of the rich culture heritage of the Chinese nation. China has gone over a long history of primitive society, slavery society, feudal society and semi-feudal semi-colonial society and the present socialist society.