China, officially the People's Republic of China (PRC), is a sovereign state located in East Asia. It is the world's most populous country, with a population of over 1.3 billion. The PRC is a single-party state governed by the Communist Party, with its seat of government in the capital city of Beijing. It exercises jurisdiction over 22 provinces, five autonomous regions, four direct-controlled municipalities (Beijing, Tianjin, Shanghai, and Chongqing), and two mostly self-governing special administrative regions (Hong Kong and Macau). The PRC also claims Taiwan – which is controlled by the Republic of China (ROC), a separate political entity – as its 23rd province, a claim controversial due to the complex political status of Taiwan and the unresolved Chinese Civil War. Covering approximately 9.6 million square kilometers, China is the world's second-largest country by land area, and the third or fourth-largest by total area, depending on the definition of total area. China's landscape is vast and diverse, with forest steppes and the Gobi and Taklamakan deserts occupying the arid north and northwest near Mongolia and Central Asia, and subtropical forests prevalent in the wetter south near Southeast Asia. The terrain of western China is rugged and elevated, with the Himalaya, Karakoram, Pamir and Tian Shan mountain ranges separating China from South and Central Asia. The Yangtze and Yellow Rivers, the third- and sixth-longest in the world, have their sources in the Tibetan Plateau and continue to the densely populated eastern seaboard. China's coastline along the Pacific Ocean is 14,500 kilometers long and is bounded by the Bohai, Yellow, East and South China Seas. The ancient Chinese civilization – one of the world's earliest – flourished in the fertile basin of the Yellow River in the North China Plain. For millennium, China's political system was based on hereditary monarchies, known as dynasties, beginning with the semi-mythological Xia of the Yellow River basin (c. 2000 BC). Since 221 BC, when the Qin Dynasty first conquered several states to form a Chinese empire, the country has expanded, fractured and been reformed numerous times. The Republic of China overthrew the last dynasty in 1911, and ruled the Chinese mainland until 1949. After the defeat of the Empire of Japan in World War II, the Communist Party defeated the nationalist Kuomintang in mainland China and established the People's Republic of China in Beijing on 1 October 1949, while the Kuomintang relocated the ROC government to Taipei. The ROC's jurisdiction is now limited to Taiwan and several outlying islands, including Penghu, Kinmen and Matsu, and it has received limited diplomatic recognition. Since the introduction of economic reforms in 1978, China has become the world's fastest-growing major economy. As of 2013, it is the world's second-largest economy by both nominal total GDP and purchasing power parity, and is also the world's largest exporter and importer of goods. China is a recognized nuclear weapons state and has the world's largest standing army, with the second-largest defense budget. The PRC has been a United Nations member since 1971, when it replaced the ROC as a permanent member of the U.N. Security Council. China is also a member of numerous formal and informal multilateral organizations, including the WTO, APEC, BRICS, the Shanghai Cooperation Organisation, the BCIM and the G-20. China has been characterized as a potential superpower by a number of academics, military analysts, and public policy and economics analysts.