Katsura Imperial Villa represents an architectural mind at the opposite pole from the tradition of heavy stone and the monumental dome: lightness, modularity, and the fluidity of space. It is era-defining not through the scale and mass of a Bilbao or a Pantheon but through the reverse — its near-immateriality.

The whole geometry of the building arises from a single unit of measure: the tatami mat. A standard tatami (about 90×180 cm) is both floor covering and the unit that measures space; rooms are defined by 'how many tatami' they hold. This modular grid binds the timber frame, the door openings, and the paper screens into a single system of proportion. Most walls are not load-bearing; interior partitions are sliding paper screens (fusuma, shōji) that can be slid aside or removed to merge or divide rooms — the plan is not fixed but a 'flexible' space that changes with use.

Its most radical feature is the dissolution of the inside-outside boundary: when the outer screens open, a room connects directly to the garden, with the space under the eaves (engawa) interlocking the two. The building does not view the landscape through a window; it settles inside the landscape. In the 20th century modern architects such as Bruno Taut, Gropius, and Le Corbusier discovered Katsura as 'modernism before modernism' — the ideals of the load-bearing frame, the free plan, the modular measure, and the unornamented surface had been realised here centuries earlier. Katsura is the summit timber architecture reaches in minimalism and flexibility.