Originally Posted by
Lord_Zed
As Goki, and Saintly have said Kyoto is pretty good for historic and cultural sites, some of the worlds best gardens, not to mention the Golden Pagoda. I'd consider avoiding going on a weekend though, the amount of tourists both foreign and local was crazy.
As far as castles go I recommend Himeji Castle in the small city of Himeji it literally dominates the landscape and is the largest remaining intact castle I believe, and national treasure to boot.
Another place I recommend visiting for cultural or nature sightseeing (though a little further afield from Osaka and Tokyo) is Miyajima. A small island near Hiroshima and home to the Itsukushima shrine which looks like it is floating during high tide, as well as an incredibly beautiful national park, filled with almost tame deer who will try to eat your map. A cable cart goes up the mountain which has an amazing view of the inland sea, as well as many monkeys and yet more deer.