Postcard showing Llac dels Pessons in the Andorran Pyrenees Mountains near the border with Spain. Part of the Madriu-Perafita-Claror Valley World Heritage site that offers a window on the ways people have lived with and in the high Pyrenees over time. The World Heritage site covers over a tenth of the entire country! That must certainly be a record. :-)
Andorra is a bit of an anomaly, truth be told. It's a co-principality – the only one of its kind in the world, in fact. It has two heads of State, the Bishop of Urgell (the next town over in Spain) and the President of France (originally the Count of Foix, the next town over in France). "Double the pleasure, double the fun", I suppose they figured back in 1278 when this system was set up. It resulted in double everything else too: two school systems, two cinemas, and, yes, two postal systems, one run by Spain and one run by France! Andorra is in fact the only country without its own postal system. There are even two sets of letter boxes around the country, and of course only French-issued stamps can go into French letterboxes (and vice versa)!
In general, I tend to see more Andorra postcards out there with French-issued stamps and I've always wondered why until I went to Andorra myself and stood in line for nearly 90 minutes to buy a stamp at the Spanish post office, whereas the French post office never had any lines at all!