Once upon a time, European borders were uprooted once more. After Napoleontic times in this case. The Vienna Treaty left a tiny 3.5 km2 parcel of land between the United Kingdom of the Netherlands and Prussia unresolved.
Noone would have ever cared, if there had not been a productive zinc mine on this parcel. Moresnet as it was called, was left as a neutral stretch for the time being, and careful negotiations began.
The zinc mine, however, was exhausted before the issue was resolved. For a while, the international Esperanto movement had great plans with stateless neutral Moresnet.
After the first world war, there were more important things on people’s minds and Moresnet was assigned to Belgium.