Taipei (, literally means "North of Tai(wan)"), officially known as Taipei City , is the capital city and a special municipality of Republic of China. Sitting at the northern tip of Taiwan, Taipei City is an enclave of the municipality of New Taipei City. It is about southwest of the northern port city Keelung. The city is mostly located on the Taipei Basin, an ancient lakebed bounded by the two relatively narrow valleys of the Keelung and Xindian rivers, which join to form the Tamsui River along the city's western border.