The zoo is really really tiny. So, if you're expecting a larger zoo, you're out of luck and will have to go to a big city, such as Chicago or Washington D.C.. Also, parking is Very limited so you'll have to park on a street somewhere if you can find a spot. The zoo shares its space with a recreation park so you're also competing for parking spaces with people going there as well.
I was really disappointed when I found many exhibits closed, and there were no capybaras out (my favorite animal) if you happen to be in Madison, make this a stop, it's free; but don't make a special trip for it if you're not close.