Great Moravia (Czech: Velká Morava, Slovak: Veľká Morava), also Moravia or Great Moravian Empire, was the first West Slavic state to emerge from "the most powerful tribal area in Central Europe". Its core territories were located on the northern Morava River along the present-day border of the Czech Republic and Slovakia. Although, its extent and location have been called into question. The rival theories place its centre at the south of the river Danube or the Great Hungarian Plain.