Jutland peninsula is made up of the German Bundesland of Schleswig-Holstein. Schleswig-Holstein has two parts: the former duchies of Schleswig (Danish fief) and Holstein (German fief), both of which have passed back and forth between Danish and German rulers several times. The last adjustment of the Danish–German border followed the Schleswig Plebiscites in 1920 and resulted in Denmark's regaining Northern Schleswig ( or more commonly today: "Sønderjylland"). The historical southern border of Jutland are areas south of Kiel, Husum and Rendsburg, but the river Eider was the border between the former duchies of Schleswig and Holstein, as well as the historical
European Plain and to the southeast - the Mediterranean basin. To the south of the Middle European Plain stretch the central uplands and plateaus of Europe elevating to the peaks of the Alps and the Carpathian Mountains. To the northwest across the English Channel lie the British Isles, while across several straits north of the Jutland Peninsula lies the Scandinavian Peninsula which is part of the Fennoscandia ecoregion. Most of the plain lies in the temperate broadleaf and mixed forest biome, while its far eastern portion extends into steppe of the ecoregion Eurasian Steppe. Beside the Great European Plain there is number