From the Wikipedia page 
Kelmis (French: La Calamine) is a municipality located in the Belgian province of Liège. As of 2011, the population was 10,881; the area is 18.1 square kilometres (7.0 sq mi) and the population density is 601.2 inhabitants per square kilometre (1,557/sq mi).
The municipality consists of the following sub-municipalities: Kelmis proper, Hergenrath, and Neu-Moresnet.
The territory around the Vieille Montagne zinc mine in Kelmis was a neutral condominium of the Netherlands and Prussia (later Belgium and Germany) from 1816 to 1919 as Neutral Moresnet, with the Mayor of Kelmis being nominated by two commissionners from the neighbouring countries. Although there were attempts by locals at making it evolve into a fully independent microstate, all of them were thwarted and it remained under double-sovereignty and neutrality until its eventual annexation by Belgium after World War I.
In the nineteenth century a Low Dietsch dialect was spoken in Kelmis. Today Kelmis is bilingual: German and French and one of the nine municipalities of the German‑speaking Community of Belgium.