The border between Croatia and Serbia in the area of the Danube is disputed. While Serbia holds the opinion that the thalweg of the Danube valley and the centerline of the river represents the international border between the two countries, Croatia disagrees and claims that the international border lies along the boundaries of the cadastral municipalities located along the river—departing from the course at several points along a 140-kilometre (87 mi) section. The cadastre-based boundary reflects the course of the Danube which existed in the 19th century, before meandering and hydrotechnical engineering works altered its course. The area size of the territory in dispute is reported variously, up to 140 square kilometres (54 square miles).