Mikimoto has been a cultivator of luxury pearls since 1893. In 2003 they commissioned Toyo Ito to design their head office in the fashionable Ginza district, Tokyo. The structure of the nine-storey building is made of steel and reinforced concrete but its character stems from the cutout detailing in the form of irregular shaped windows sporadically placed on the facade.
The concept is based on a building that is suspended by its facade, leaving the internal spaces column-free.
The building has an apparent simplicity, comprised of a prism perforated by a series of irregular windows, like a Swiss cheese. These holes appear to be arranged at random. However, since some of these are placed in the corners (where typically would be a column) there is a sophisticated construction system to enable such a facade.
Because of the design, it required a strong structure that would allow for freely placed openings, but at the same time the material needed to not easily expand when heated. For this reason Ito opted for a mixed system of metal plates and concrete. Steel plates of 1.2 cm were prepared and fixed by a web of studs in order to maintain a uniform thickness of 20 cm, and then concrete was poured between them.