At the Congress of Vienna in 1815 many borders and countries changed. One of the borders was the one between the new United Kingdom of the Netherlands and Prussia. For the most part Prussia and the Netherlands agreed on the border, because it was mostly the same as the old border. Around Moresnet there was a problem. Between the villages of Moresnet and Neu-Moresnet was the zinc mine of Vieille Montagne (in French) / Altenberg (in German). Both countries wanted to have this mine. In 1816 it was decided that the village of Moresnet itself would become part of the Netherlands, Neu-Moresnet would become part of Prussia and the mine and the village of Kelmis around it would become neutral territory where both countries shared the power.