The concept of the schema grammar, in which a set of schema rules represents regularities hidden in the architectural space, is proposed. The schema as a conceptual image is transfigured by rules, and finally becomes a architectural space. By constructing the grammar, it is possible to understand an invisible structure of space. For confirming effectiveness of the grammar, we attempt to obtain a grammar of the ancient city plans in China and Japan. The grammar have been derived from the ideal concepts in the ancient time. Comparing the rules and production processes, we can show the distinctions of ideal concepts on cities in both countries.
