Osaka is the port town on the island of Honshu, the capital of the prefecture and the third-largest city in Japan. With a population of 2.5 million, the city, which is surrounded by satellite towns, lies at the estuary of various rivers in Osaka By. In early history Osaka was the seat of the Japanese emperor several times. The city is seen as a centre of industry, trade, culture and research (5 universities, various research institutions). The Daimyo castle dating from the 16th century, the many temples and gardens are all worth a visit. The most important sectors of the economy here are textiles, iron and steel, machine manufacturing, the chemicals industry and the oil refineries. Many prospering companies have their headquarters in the city, laying the foundations for a modern infrastructure and cultural tradition. In 1970 Osaka hosted the World's Fair. The city is currently experiencing somewhat of an architectural renaissance, with the objective of making it a focus for people, goods and information from all over the world.