What a pleasant question...
I am ruling out the Vatican because I don't believe it is counted as a country/nation ( I chose my words carefully). It is a city/state which isn't the same thing. According to Wikipedia, sometimes dubious I know, Monaco is in fact the capital as well as the country. I do count the USA as a country with a capital, I will have to look at the Washington facts as tbh it is the first time I have heard Markabilly's point. So, will keep checking to see if anyone gets the answer soon. :)