Vieille Montagne was a zinc mine in Kelmis, a town in Belgium between Liège and Aachen. The mine's name is French for "old mountain" or "old mine", and this is also reflected in its German name, Altenberg. The mine was once a bone of contention between Prussia on the one side and the United Kingdom of the Netherlands on the other, that resulted in a piece of land that became the territory of Neutral Moresnet.

Neutral Moresnet was a small Belgian–Prussian condominium in western Europe that existed from 1816 to 1921 and was administered jointly by the United Kingdom of the Netherlands and the Kingdom of Prussia. It was 1.5 kilometres (1 mi) wide and five kilometres (3 mi) long, with an area of 360 hectares. After 1830, the territory's northernmost border point at Vaalserberg connected it to a quadripoint shared additionally with the Dutch Province of Limburg, the Prussian Rhine Province, and the Belgian Liège Province. Its former location is represented presently by the Three-Country Point, the meeting place of the borders of Belgium, Germany, and the Netherlands.