Neusiedler Lake (noiˈzēdlər) [key], Ger. Neusiedlersee, Hung. Fertő tó, c.130 sq mi (340 sq km), on the Austria-Hungary border SE of Vienna. The lake's area and depth (average 5 ft/1.5 m) vary considerably with the seasons. The heavy growth of lake reeds supplies the Austrian cellulose industry. Carp fisheries are in the lake. Its lonely and desolate salt marshes attract a variety of wild life and have been protected since 1935. The Neusiedler region has noted resorts. There are remains of prehistoric lake dwellers in the vicinity.