sentences:  The four main wine regions are split into 16 districts.This narrow valley of the Danube around Melk is reminiscent of the great wine areas of the Rhine, with steep terraces that produce world-class Grüner Veltliner and Riesling wines.Climatically and geologically it marks the transition from the Alps to the Hungarian plains, leading to a diverse array of microclimates and terroir, with the river moderating the effects of the cold Alpine winds.