Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of China, Korea, and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea in the south. Its capital is Tokyo. It encompasses over 3,000 islands, the largest of which are Honshū, Hokkaidō, Kyūshū and Shikoku. Most of Japan's islands are mountainous, and many are volcanic, including the highest peak, Mount Fuji. It has the world's 10th largest population, with nearly 128 million people. The Greater Tokyo Area, with over 30 million residents, is the largest metropolitan area in the world. Archaeological research indicates that people were living on the islands of Japan as early as the upper paleolithic period. The first written mention of Japan begins with brief appearances in Chinese history texts from the 1st century AD. Japanese history has been marked by alternating periods of long isolation and radical influence from the outside world. Its culture today is a mixture of outside and internal influences. Since it adopted its constitution on May 3, 1947, Japan has maintained a unitary constitutional monarchy with an emperor and an elected parliament, the Diet, which is one of the oldest legislative bodies in Asia. Japan is an economic world power with the world's second largest economy, and is the sixth largest exporter and importer and is a member of the United Nations, G8, G4, and APEC.