A beer at the bar in Belgium, to the toilet in the Netherlands.

Nestled snugly between the second and third bulge at the very top of the province of Antwerp is Baarle-Hertog-Nassau, five kilometres from the border. A mosaic of twenty officially recognised Belgian enclaves completely surrounded by the Netherlands and a dozen Dutch enclaves, haphazardly scattered between pieces of Belgium.

There are 2,500 Belgians living in Hertog and 6,000 Dutch in Nassau, in one double village with two names. There are two municipalities with their respective town halls, two provinces, two nationalities, two royal houses, two tax systems, two bishops, two churches close to each other, a Dutch and a Belgian police station, two fire brigades, two post offices, two schools, two power stations, two ... Just about everything in duplicate, so to speak. Before the introduction of the euro in 2002, shops accepted cash payments in both Belgian francs and Dutch guilders, so that the people of Baarle-Hertog-Nassau had a stock of each.

Are you still with me? Good, because there is still a lot more to the two-country puzzle. In the street pattern, the enclave boundaries are clearly visible. When out walking, you notice that you cross the border when you cross the street or go around the corner, for example. The house numbers indicate whether you are walking past a Belgian or a Dutch house. The location of the front door determines the nationality of the house. Belgian houses have a black number on a white background and the Belgian tricolour in the top left. Dutch ones have a blue number on a white sign, with a vertical stripe on the left and a blue one on the right. But it gets even more crazy! Some houses are partly on Belgian soil and partly on Dutch, because the border runs right through the front door. These houses carry both a Belgian and a Dutch number. In addition, both countries have their own numbering. Like the former café 't Hoekske, on the corner of Nieuwstraat and Stationsstraat, where the border ran right through the bar. There was a practical advantage to this. For the sale of partly Belgian and partly Dutch plots of land, two notaries were required, each of whom had exclusive legal authority within their own state borders. This café was very suitable for that. Unconfirmed sources even let the border run right through the toilet in one house, so you can answer the call of nature with one buttock in Belgium and the other with our northern neighbours. Anyway, the result of all this is that you cross the Belgian-Dutch border dozens of times, in record time, without even noticing.

The key question now is: what is the cause of this international tangle? In 1198, Duke Hendrik I of Brabant lent part of Baarle to the Lord of Breda and the Count of Nassau. The taxable goods that his subordinates had already borrowed were not covered by the division. This situation was later confirmed repeatedly in official documents, despite several attempts to exchange territories.