Why it's the capital
It has been the main town of Andorra since 1278, when the French co-prince and the bishop co-prince agreed to share power over the country.
Capital of AndorraHigh in the eastern Pyrenees between France and Spain, Andorra la Vella sits where two mountain streams, the Valira del Nord and the Valira de l'Orient, join to form the Gran Valira river.
It has been the main town of Andorra since 1278, when the French co-prince and the bishop co-prince agreed to share power over the country.
Find the Pyrenees, the mountains between France and Spain, and aim at their eastern part: tiny Andorra is tucked in there, with its capital inside it.
Sources: Wikipedia: Andorra la Vella