We have made a computer graphics model of Chang'an City when it was the capital of China during the Tang Dynasty (7-10th century). The real-time rendered images are projected onto a hemispherical screen by 6 projectors after being geometrically transformed, and the brightness and color adjusted to produce one seamless image on the screen. The transformation is executed on our proprietary image processors. The walkthrough systems are linked between Japan and China through the internet. An authority on Chang'an studies based in China, walks through the virtual world while explaining for students in Japan. The image in the immersive environment is synchronized to the motion of the guide. To compensate for the delays or for packet losses over the internet, the optimal motion of the student viewpoint is estimated based on received sparse information, educational knowledge, and heuristics that predict the guide's next destination. Key words: Hemispherical Screen, Immersive Pr...