Wikipedia
The Rhine-Neckar Metropolitan Region (, ), often referred to as Rhein-Neckar-Triangle is a polycentric metropolitan region located in south western Germany, between the Frankfurt/Rhine-Main region to the North and the Stuttgart Region to the South-East.
Rhine-Neckar has a population of some 2.4 million with major cities being Mannheim, Ludwigshafen and Heidelberg. Other cities include the former Free imperial cities of Speyer and Worms. The metro area also encompasses parts of the picturesque Baden and Palatinate wine regions, the second largest vine region of the country called Deutsche Weinstraße and territory from the three federal states of Baden-Württemberg, Rhineland-Palatinate and Hesse. It has a strong local identity as a successor of the historical Electorate of the Palatinate state.
The region is named after the rivers Rhine and Neckar, which join at Mannheim. Since 2005, the region is officially recognized as a European Metropolitan Area. After its classification as a European Metropolitan Region and the signing of a second interstate treaty between Baden-Württemberg, Hesse and Rhineland-Palatinate, in 2006 the close collaboration between the public sector, industry and science was institutionalised in a private-public-partnership model that is one of a kind in Germany: ever since, the associations Zukunft Metropolregion Rhein-Neckar e.V., Verband Region Rhein-Neckar and Metropolregion Rhein-Neckar GmbH have stood for targeted, harmonised regional development work.