Double curvature.

A museum on the island of Shikoku, Japan, hugs the contours of its mountain site and celebrates the organic through form, materials and contents.

Makino Museum of Plants and People is spread over the gentle slopes of Mt Godai above Kochi City on the island of Shikoku. Designed by Naito Architect & Associates, the place is dedicated to the memory of Tomitaro Makino, eminent scholar and father of Japanese botany. This inspiration, the museum s botanical purpose, and the fact that Kochi Prefecture is an important timber-producing region, suggested wood as the main material for construction, and Naito's manipulation of it has produced structures of extraordinary poetic power.

Because of complex land ownership the museum was split into two parts: a museum with research facilities and an exhibition hall; with the two linked by a 170m corridor.

To disturb the landscape as little as possible, both buildings are low and sinuous, their organic forms hugging the mountain contours so that they seem almost a part of the topography. Such forms present little resistance to the salt-laden winds to which the site is exposed and construction takes account of the region's occasionally severe storms. Neither building is taller than surrounding trees.

The site, an angular S-shape, stretches across the mountain from the museum on the west to the laboratory on the east. Both buildings, each on plan looking like a fossil, wrap round a central courtyard and are covered with continuously curving roofs. Spun round the courtyards are galleries, cafes meeting rooms, offices and so on. The museum is equipped with a laboratory, library and studies.

Enclosing the buildings with sinuous walls of reinforced concrete, hollow steel sections form ridges, eaves and columns, spanning between ridges and eaves with laminated wooden beams of Douglas fir. The roofs' complex geometry meant that each beam is different, connected at the ridge by cast metal joints which allow for variations in angle. During design, wind-tunnel tests, simulating the effects of a severe typhoon, were carried out, exerting a pressure of over a ton per square metre on parts of the roofs and building frames adjusted accordingly. Roofs are typhoon-proof with laminated panels of zinc and stainless steel, their unique dimensions and forms achieved by computer-aided design. As a further precaution against Kochi's winds and rain, the architects devised a special guttering system between each panel.

Sensually the interiors and exteriors of the buildings are distinct. Externally, the smooth silvery forms of the roofs emerge from vegetation in serpentine manner. Internally, the wonderful scale and articulations of the sweeping roof dominate. Unlike its cool external carapace, its underside is warm and red, sheathed in the inner surfaces of Kochi-grown Japanese cedar (sugi). The upper level of the main museum building extends out onto a deck where the wood changes in response to the roof covering, to local silvery Japanese cypress (hinaki).