Liu Zhongwen shows his handmade miniature waterwheel in Lanzhou city, capital of Northwest China's Gansu province, June 10, 2017. Since the Ming Dynasty (1368-1644), waterwheels have been popular along the Yellow River in Lanzhou city to irrigate fields. Liu, who is in his seventies, is interested in studying and making small waterwheels without using any nails. His creations range in size from 12 centimeters to one meter in diameter. [Photo/China News Service]