Columbia subject headings:
Landscape architecture--Germany--Emscher River Valley (North Rhine-Westphalia)
Parks--Germany--Emscher River Valley (North Rhine-Westphalia)
Parks--Germany--Ruhr (Region)
Harvard subject headings:
Landscape architecture--Germany--Emscher River Valley (North Rhine-Westphalia)
Parks--Germany--Emscher River Valley (North Rhine-Westphalia)
Parks--Germany--Ruhr (Region)
Princeton subject headings: