@Tim Brown and I were quite amicable when it came to choosing the 80 zoos and for sure the zoo that was closest to making the cut was Franklin Park. It's in a major city (Boston), has a big tropical house, and has a nice new outdoor gorilla complex that looks impressive. In truth, there weren't any other zoos that we strongly considered.
Which zoos would have missed out if you had only included, say, 70?