Guangdong (alternately romanized as Canton Province or Kwangtung) is a coastal province in South China on the north shore of South China Sea. The capital of the province is Guangzhou. With a population of 113.46 million (as of 2018) across a total area of about 179,800 km (69,400 sq mi), Guangdong is the most populous province of China and the 15th-largest by area. Its economy is larger than that of any other province in the nation and the 6th largest sub-national economy in the world with a GDP size of 1.47 trillion US dollars (9.73 trillion Chinese yuan) in 2018. The Pearl River Delta Economic Zone, a Chinese megalopolis, is a core for high technology, manufacturing and foreign trade. Located in this zone are two of the four top Chinese cities and the top two Chinese prefecture-level cities by GDP; Guangzhou, the capital of the province, and Shenzhen, the first special economic zone in the country. These two are among the most populous and important cities in China, and have now become two of the world's most populous megacities.