oh wow... hmm...how do I answer this?? We live a short metro ride away from the National Mall - when I first got here and people told me to go visit the Mall, I rolled my eyes. I hate going to the mall. I avoid it in every way possible. Only to realise the National Mall is in Washington DC and the whole stretch a mile and a bit (maybe less or more?) has a bunch of Smithsonian Museums. And they are all FREE!! 

So, picking the best museum is going to be hard!! I have yet to visit the new one - African American Smithsonian. From what I hear, it's supposed to be really great! 

Of the paid ones, I have been to the Spy Museum and the Newseum. I have to say, I did very much like the Newseum (it's going out of business though). I do think they priced it high - when you have all these free museums, anything would feel too high! Newseum tries to compensate by letting you come the next day - which is silly because most tourists come here for a short time and they don't get time to revisit a museum - even the free ones!!

Anyway - it was a great exhibit and I really liked it. The other one I really liked was the Holocaust Museum. I wish it didn't need to exist. It's a constant reminder of how horrible humans can be. I thin everyone should visit it at least once. It's moving. 

I guess, I failed answering this question. I can't pick one best museum. The Vatican Museum is fantastic!! Mindblowing! But come on - that's hard to compete with!