I didn’t realise the Schengen agreement was over 30 years old; I always thought it was from the late 90s or 2000s although that may well be the time when the European nations actually started removing border control infrastructure (as opposed to just idealistically talking about it).
The pictures in the link below below appear to have been taken by someone looking for pretty/arty shots and omit many more equally peaceful (in political terms) border areas but maybe not as pretty (due to traffic, roads etc) – such as DE/DK border along the Flensborgvej which I was looking at a few weeks ago and wondering whether it is legal to ride an e-bike across there (assuming you have correct ID documents valid for the EU and the E-bike is compliant, which mine is)
There is a DE/DK border shown in some field with a sheep in it (presumably the eartags, registration and sheperding procedures are closely linked between DE and DK, as if the sheep walks just 3 metres it is in another country!)
How long Europe will remain like this is another matter entirely (although UK is the only country at present to actually vote itself out of the EU and never signed the Schengen agreeement in the first place there are other countries nearer the Middle East where things aren’t as peaceful).
What Peaceful Borders Between European Countries Look Like | Bored Panda