This is exceptionally cool:
It's a real-time 3d interactive walkthrough of Matsumoto-jo castle. It requires Adobe Shockwave to view.
It was selected as a New Tech Demo at SIGGRAPH last year. A word from the author:
As far as my work is concerned, Matsumoto-jo will be the first in a series of online interactives on world cultural sites. In the near future, look for 3D interactives on the Maya, Rome’s Colosseum, Masada, Dun Aengus, and Alhambra.