In the map it can be clearly seen that the unemployment is higher in Wallonia than in Flanders. This is largely due to the fact that Wallonia has historically relied on its heavy industry, such as steel and coal, which has moved abroad the last decades. In fact, the Sambre and Meuse valley which was the industrial heartland in Belgium thanks to its coal resources, can be clearly seen on the map.
It is also interesting to see how the distribution of unemployment has changed throughout the years, as seen on these maps:
The area used be be a huge industrial area, which then suffered from desindustrialisation
You have similar areas in the north/east of France