Between 2009 and 2012 flora and vegetation on the site of the former coal mine and coking plant “Hansa” in the city of Dortmund in the Ruhr Area (North Rhine-Westphalia) were investigated intensively. Further, historical and recent floristic literature about the site was evaluated. Evidence is provided on 482 taxa of vascular plants on the investigated site, including a number of endangered, rare, typical industrial and anecophytic taxa. Vegetation types on the brownfield site range from early pioneer states to young shrub and forest stands. Anecophytic poplar stands are a characteristic vegetation type on urban-industrial derelict land in the Ruhr Area. Relevés of these poplar stands were performed in order to characterize this plant community. The value of the species-rich flora of the investigated brownfield is discussed in relation to the urban biodiversity of the metropolitan Ruhr Area.