It's probably some kind of sport for any child in the world but for Düsseldorf turning cartwheels has been a tradition for a many centuries. It was entertainment for visitors of fairs and festivities and begging at the same time - the boys would get a penny or two for each cartwheel.
Today the Radschläger have become a symbol for Düsseldorf, with monuments all around the city, made of cake, the fountain (in the picture), songs, and an annual tournament on the Kö. And girls are allowed these days as well.

