China is planning to create the worlds biggest mega city by merging nine cities to create a metropolis twice the size of Wales with a population of 42 million, reported Telegraph on Monday. City planners in south China have laid out an ambitious plan to merge together the nine cities that lie around the Pearl River Delta. The Turn The Pearl River Delta Into One scheme will create a 16,000 sq mile urban area that is 26 times larger geographically than Greater London, or twice the size of Wales. The new mega-city will cover a large part of Chinas manufacturing heartland.