The National Zoo in a long time and even though it was getting into late afternoon we figured why not, it's free and worse case we see one or two things and then go find something else to do. We had already walked quite a bit anyways, no need to walk the entire zoo.
Spoiler: we walked the entire zoo. Also? It's in a straight line. And if you enter from the "official" start of the zoo, which is where you'd enter if you took Metro there (which we did), it's downhill the entire way. Which means it's uphill to get back. Who planned that? Seriously.
I didn't have my bigger zoom lens because it's heavy and I was carrying around two other lenses, so my animal pictures weren't all that impressive. But I'm going to share them anyways because that's what I do.
Overall a great zoo trip!