We know we do not know everything about economy. But, where is the shadow economy? Is this more concentrated in poorer or richer regions? In cities or rural areas? In a previous project, we mapped the use of large banknotes as a proxy to identify the shadow economy that we conceptualised as ‘unregistered’ economy, i.e. it might include both illegal and legal activities. So far, we were able to identify a higher concentration of large banknotes in urban, richer and ‘white’ neighbourhoods. In the future, we would like to expand the scope of research beyond Brussels and include time dynamics. Comparative approaches with countries would be welcome.