Designation for the dry wines of the highest level in the VDP classification model (see there the regulations in detail). The spelling with "ss" instead of "ß" is done intentionally with regard to international marketing. It applies to all growing areas with the exception of the Rheingau - here, they are called Erstes Gewächs. The Rheingau VDP members are an exception; since the 2013 vintage, they are allowed to call their dry top wines from the "VDP.GROSSEN LAGEN®" "VDP.GROSSES GEWÄCHS®".
The designation "Großes Gewächs" (here, however, with "ß") is also used in the Bernkasteler Ring association, but it has no connection with the VDP classification.