My mother recently took our family to the Indianapolis Children's Museum. We had been when my son was 18 months old, he's 13 now, so it had been awhile. This is a fun museum for the kids. My three year old had a lot of fun in the toddler room, they an elaborate water play system. She got soaking wet, so next time I think I would bring her a change of clothes. Aprons are supplied for the children to wear, but we are talking little kids here, they are going to get wet. Next to the water works is a sand table, wet kids in sand, nice combination.
The museum has a pretty cool dinosaur exhibit as well. Kids can put on goggles and dig for dinosaur bones. All of my kids had fun doing that.
There are many other fun activities to do at this museum. We got there shortly after they opened (we would have gotten there when they opened, but we got a bit lost) and we didn't leave until they closed. Which, reminds me of another fun thing. When they were closing, they got everyone to stand around the staircase (it's kind of a spirally ramp actually) and count down to closing. They gave most of the kids a flag to hold and wave, and then we all marched down the ramp in the "parade". My three year old got to hold a flag, and she thought it was wonderful. While we were walking down the ramp, the employees stood by waving, and we all chanted, "Come Join the Parade, come join the parade." At least, that's what my three year old told me they were saying, and that's what we were chanting! It was a fun way to end out day, and Lydia (three year old) still likes to talk about it.