Please visit Osaka castle. http://www.japan-guide.com/e/e4000.html
You will see not only see the castle tower but also the Nishinomaru Garden with some 600 cherry trees. If you go there in early spring you can see an ume (plum) orchard boasting 1,270 ume trees in 100 varieties, and other spots where visitors can enjoy seasonal flowers. The Osaka Castle Band Shell and Osaka-jo Hall are popular venues for music concerts.