I brought my 7 year old son to the Kids Plaza Osaka, and he thoroughly enjoyed himself.

Very little is known about this place - as it is not high on the tourist agenda. But it is a pretty good children's museum for kids under 12. One floor is dedicated to younger kids - where they can pretend to run a super-market, be a postman or fixed some pipes. Even though my son is little old for this, he still enjoyed it - especially the super-market, where as the cashier he could scanned the bar codes and print out receipts!

Another floor is dedicated to older kids where there are science experiments etc. There is section on soap bubbles, and in one particular exhibit you can almost enclose a child in a soap bubble. There is also a section on animation, and a TV studio where you can read the news (in English, Chinese or Japanese). They will video it and let you watch the video a little while later.

We spent about 2.5 hours there, but my son could have easily spent an entire morning or an entire afternoon at the place.

very near to subway Ogimachi Sta station, open 9am to 5pm and weekend till 7pm, kids can run freely in this 4 storey playground which consists of some science experiment, they even have a mock up radio station where kids can be a broadcaster. Awesome...and reasonable price 1200yen for high school and above, for kids is 600yen. Children can easily spent the whole day here.