Past, present and future: The evolution of China's incredible high-speed rail network

Over the last decade China has built the world's largest dedicated high-speed rail network, revolutionising long-distance travel across this vast and diverse nation. But there's still plenty more ground to cover.

(CNN) — At the beginning of the 21st century China had no high-speed railways. Slow and often uncomfortable trains plodded across this vast country, with low average speeds making journeys such as Shanghai-Beijing a test of endurance. Today, it's a completely different picture. The world's most populous nation has -- by some distance -- the world's largest network of high-speed railways.