My kids love the Indianapolis Zoo very much! This zoo is not too huge or too small, just right size, in my opinion. Especially, it feels just right size for small children. The new dolphin exhibit just opened, and I can't wait to go see! The Dolphin Adventure Dome makes you feel like you are under the water.
Inside the zoo, you also can ride a train and can play at a playground area. We are taking our 1-year-old son to the zoo as his 2nd birthday party. Great zoo!
UPDATE- We went to the zoo last Monday (8/8/05). It was great fun! The dolphin exhibit is amazing. You feel like you are inside of ocean swimming with dolphins. If you are planning to visit more than twice in a year, I highly recommend buying yearly memberships. If we pay regular one time only addmission fees, it costs about $40 for us (2 adults + 2 year-old and 4 year-old). We bought a family membership which is good for 2 adults and all children in the household (we have 2 kids). It costs $75, but parking is always free for members. If you are not a member, you have to pay $5 for parking. When we entered the parking area, we go ahead paid $5 for parking. At the zoo entrance, we showed the parkikng recipt when we bought the membership and got $5 off of $75 membership fee. Also, we found a $5 coupon for zoo membership from one of coupon mailers we got at home. I don't remember which coupon mailer it was in, but you might be able to find $5 coupon somewhere. It was great deal to pay only $65 for yearly fun at the zoo.