Kaohsiung is a city located in southwestern Taiwan, facing the Taiwan Strait on the west. Kaohsiung, officially named Kaohsiung City, is divided into thirty-eight districts. The city is one of five special municipalities of the Republic of China (Taiwan). On December 25, 2010, it merged with Kaohsiung County of Taiwan Province to form a larger municipality. Kaohsiung is the second largest city in Taiwan, with a population around 2.9 million. It is a center for manufacturing, refining, shipbuilding, and other light and heavy industries. A major port, through which pass most of Taiwan's marine imports and exports, is located at the city but is not managed by the city government. Kaohsiung International Airport serving the city is the second largest airport in Taiwan. The Port of Kaohsiung is the largest harbor in Taiwan. Kaohsiung is the terminal of the Sun Yat-sen Freeway. The city is served by the railway stations of Western Line and Pingtung Line. Taiwan High Speed Rail connects it with Taipei City. The Kaohsiung Mass Rapid Transit, the city's subway system, was launched in early 2008. Kaohsiung was the host city of the 2009 World Games, a multi-sport event primarily composed of sports not featured in the Olympic Games. The city is also home to the Republic of China Navy.