What is "vennbahn"

The Vennbahn (, "Fen Railway") is a former railway line that was built partly across what was then German territory by the Prussian state railways. It is now entirely in Belgium, because the trackbed of the line, as well as the stations and other installations, were made provisional Belgian territory in 1919 (permanent in 1922) under an article of the Treaty of Versailles.

This had the effect of creating six small exclaves of Germany on the line's western side. The treaty (not the location of the trackbed, per se) also created one small Belgian counter- enclave, a traffic island inside a three-way German road intersection near Fringshaus.