I love taking the boys to our zoo. We live close enough to make having a membership worth it, and it really is one of the best zoos I've ever gone to.
The boys love the zoo, too. There are lots of places to play throughout the zoo, in particular Nature's Neighborhood where they get to explore different things in the environment. Joshua's favorites are the seals, the polar bears, the elephants, the hippos, the birdhouse and the monkeys - really, all of it. And they're redoing the aquarium right now to one of those glass dome styles you can walk through and under. :)
There really is lots to say about this zoo, but then I would take up a lot of space with words and no pictures!
Lunch on African Safari.
Stopping to play with a lion cub.