Huaihai, economic hub around Xuzhou 徐州[Xu2 zhou1], including parts of Jiangsu, Shandong, Henan and Anhui provinces
Definitions (Wiktionary)
name
Huaihai, a name for the area surrounding modern Xuzhou city, to the north of the Huai River and to the west of Lianyungang city (formerly Hai prefecture)