When Germany invaded Belgium during the First World War, the Belgian parts of Baarle presented a bit of a problem for the Germans, because they were surrounded by neutral Dutch soil. Thus the Baarle-Hertog became a key strategic place for the Belgian army.
Perhaps the most impressive act of rebellion was when the army smuggled in a complete communication array, pretending that it was part of the equipment used to build a refugee camp. Some of the materials smuggled in included zinc plates for grounding and dozens of 18-meter (59-foot) ship masts, which were transported to the station by a local craftsman in his handcart. When complete, the Zendstation MN7 boasted a 40-meter (131-foot) central antenna mast, which was used to exchange messages with the Belgian resistance and to jam German communications.
The station was a real problem for the Germans, but there was nothing that they could do due to the neutral Dutch land that surrounded it. Plans were even made to bomb the radio station, but they were eventually scrapped because the location was wedged between Dutch land on three sides and it would be impossible to not hit them. The mast was taken down not long after the war ended, with nothing preserved except the memory of how it was brought in.
But nearly a century later a replica was commissioned by the Amalia van Solms Society and the local tourist bureau as part of a larger walking route exploring the history of World War I in Baarle-Hertog. The mast was finished and unveiled in 2014. It is purely decorative and does not have any working elements, but does resemble the original quite well.
You can see the Dutch-Belgian border close to the mast.
Know Before You Go
The mast is freely available.