Neckarsulm (German pronunciation) is a city in northern Baden-Württemberg, Germany, near Stuttgart, and part of the district of Heilbronn. As of 2004, Neckarsulm had 27,296 inhabitants. The rivers Neckar and Sulm join there, hence the name, which is often misunderstood or mispronounced as "Neckars Ulm", an incongruity that would mean the Ulm of the Neckar, as the city of Ulm is well to the east on the Danube at the border between Baden-Wuerttemberg and Bavaria. Neckarsulm is famous for being ranked first in the German Solarbundesliga (cities beginning at 10,000 inhabitants), a competition in renewable energy installations. Its other fame is that the Neckarsulm-Gundelsheim Weingaertnergenossenschaft (vintner's co-operative) is reputed to be the oldest in Germany; trollinger and lemberger are the principal varieties of grape that are grown.