San Marino is the oldest existing Republic in the world. This is not just some boast, but historical fact. The beginnings of San Marino, as befits any good story, are shrouded in legend, putting the founding of the city into the hands of a saint, St Marinus. Like most of the early and many of the later Catholic saints, he is mythical but features a nice story.
Among the dwarf states of Europe, the Principality of Andorra is the largest. Until quite recently, it was an absolute monarchy. It was governed not by one, but two princes, and both are not citizens of Andorra. They don't even live in Andorra. To make the case even more curious, it is not a hereditary monarchy.