Wuppertal is found on the densly populated banks of the River Wupper, a tributary to the Rhine. It is a city of 355 000 people. It was founded in 1929 by merging Elberfeld, Barmen, Rosdorf, Cronenberg, and Vohwinkel. It is considered one of the greenest cities in Germany. There are two-thirds of the city is green space. It is, at most, a 10 minute walk to any public park or woodland path. Today Wuppertal is a major industrial centre to textiles, metallurgy, chemicals, pharmaceuticals, electronics, automobiles, rubber, vehicles, and printing equipment. Aspirin originates from Wuppertal. In was patented by Bayer in 1897.