Vennbahn – The Vennbahn (German pronunciation: [ˈfɛnbaːn], “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.

Vennbahn – Wikipedia

https://en.wikipedia.org/wiki/Vennbahn

The Vennbahn (German pronunciation: [ˈfɛnbaːn], “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.