China is the third largest country in the world and, with more than a billion people, is home to 20% of the world's population. Traveller Justine Shapiro explores the traditional southwest of China, the autonomous region of Guangxi and the provinces of Yunnan and Sichuan, while Megan McCormick journeys through central China from Shanghai to the Yellow Mountains, and from the Yangzi River to Xi'an, the ancient capital of China.