There was a moment in DC when I walked out of the hostel to explore, made it about three blocks and almost collapsed from fatigue, nausea and gut pain. Food poisoning had hit me pretty hard. I limped into a coffee shop and sat in a comfortable chair until the worst of it went past. 24 hours later and the food poisoning (or whatever it was) still hit me hard.
I was still so sick the day that I left DC that I meant to go to several museums - the Smithsonian, the aerospace museum, DC is full of fascinating things and I wanted to see some of them. Nausea and pain were not cooperating with this plan. I took two steps into the US Postage museum because it was the closest one to the hostel, and then when I had no interest at all in its contents I limped to the museum of art (the next closest, which I also had no interest in).
In the end, I just got onto a train and left DC. Getting sick stole that experience. To get it back, I'll need to go back to DC.
6 hours on the train seemed easy. Next stop, New York City.