Slightly off topic, but still an 'Odd Border Crossing' was an experience that I had on a train on an Austrian branch line. It was a long time ago, so I cannot remember exactly where this was, but it was the border between Austria and Hungary which, at that time, was behind the Iron Curtain.
The train stopped at the border and heavily armed Hungarian soldiers got on. The train was searched and the doors were locked. We then set off with the armed guards on the end balconies of the coaches. After a short while, we stopped at a station which served a small village. However, the village was a little way from the station and over the border back in Austria! At the time the line was built, of course, it was all part of the Austrian - Hungarian empire so there was no border between the station and the village.
The soldiers carefully checked the papers of those wishing to leave the train and, once satisfied that they were indeed genuine Austrian villagers, allowed them off and escorted them to a locked gate. This was unlocked and they were allowed through to cross a footbridge over a small stream which had unwittingly become the Iron Curtain. A small group of Austrians waiting for the train were then, having had their papers checked, allowed through the gate and escorted to the train. While all this was going on, some of the soldiers remained on the train standing menacingly in the doorways.
The gate was re-locked and the soldiers locked us all in the train again before taking up their positions on the end balconies. The train continued on its way until it reached the point where the line crossed back into Austria again where the train doors were unlocked and the soldiers got off, no doubt to repeat the process on the next train to go the other way.
