A summer pavilion usually provides three basic amenities: seating, shade, and shelter. From a distance, it is unclear whether Sou Fujimoto’s Serpentine Pavilion, which seems to hover atop a clearing in Kensington Gardens like a lost cloud, can supply any of these. Upon closer inspection, thin, white chair legs begin to stand out against a backdrop of over 26,000 thin, white steel supports. Steps coupled with railings and ledges that provide additional seats can be spotted in the gridded structure, which overlays the surrounding vegetation like a futuristic fantasy. Visitors are swathed in criss-crossing linear shadows. Circular sheets of transparent polycarbonate catch raindrops on rainy days, and reflect sunlight on sunny ones.

Similar to the previous 12 pavilions that have adorned Serpentine Gallery’s lawn since 2000, Fujimoto’s pavilion refuses to be just a pavilion. Rather, over the course of its four-month run, it aims to push forward radical ideas about architecture. Serpentine Gallery does not intend for this award to discover unknown talents—each of the former recipients, which include fellow Japanese architects Toyo Ito (2002) and Sanaa’s Kazuyo Sejima and Ryue Nishizawa (2009), had already garnered international acclaim prior to being commissioned. Fujimoto, now 42, is the youngest appointee to date. The eligibility, however, is narrowed to those who have not yet realized a project in the UK. Therefore, this public installation is for architects a steppingstone towards future work, as well as a magnified presence, abroad. But this prestige comes at a cost—the commission is unpaid and demands a tight schedule. After finalizing the design concept in the first month, Fujimoto’s office in Tokyo collaborated with London-based engineers around the clock on opposite sides of the globe in order to squeeze the design and construction into a mere five months. For an office with fewer than 15 employees like Fujimoto’s, this entails a commitment to a string of long nights and working weekends.

Needless to say, constructing a cloud out of steel and glass requires a heavy dose of intricate detailing. The pavilion’s basic unit is a rectilinear form fashioned out of 20-mm-wide tubular steel. Repeated over and over, this produces an inhabitable grid that weighs over eight tons. Despite the apparent simplicity of this basic unit, its complex assembly proved to be a significant challenge for the structural engineer, even forcing a system upgrade after structural calculations initially brought their computers to a standstill. This complexity largely results from Fujimoto’s contortion of the grid, which successfully mitigates its inherent rigidity. In some places, it seems to be incomplete or hollowed out, which creates a variety of densities. By strolling around the pavilion, views of the surroundings become alternately obscured and framed by dense clusters of steel. On cloudy days, it seems to dissolve like a chameleon into the cumulous forms above.

Minimalist forms and a monochromatic palette are commonly associated with contemporary Japanese architecture and design. White cubes, in fact, show up repeatedly in Fujimoto’s oeuvre, but his white cubes do not fit the conventional definitions supplied by his predecessors. Since the founding of Fujimoto’s atelier in 2000, cubes have been interlocked, stacked, and even nestled inside one another in order to create so-called “primitive” architectures. Fujimoto’s first monograph, Primitive Future, opens with a juxtaposition of two drawings: Le Corbusier’s “machine for living in” is labeled as a “nest” and a sketch by Fujimoto himself of stacked planes floating at 35 cm increments is labeled as a “cave.” Similar to his conceptual sketch for the Serpentine Pavilion, people on the drawing seem to float behind hovering planes. Fujimoto explains, “Le Corbusier, who proclaimed ‘Machine for Living,’ devised a nest for people… I envision architecture as a cave immediately before becoming a nest. It is not organized in the name of functionalism, but by place-making that, encourages people to seek a spectrum of opportunities. Instead of oppressing functions, the cave is a provocative and unrestricted milieu.”

Although the international press is clearly enamored by the image of Fujimoto’s pavilion as a cloud, the actual experience of the pavilion can also be likened to that of a cave. Aside from the handful of chairs inside, there are no clearly defined seating areas; visitors must search for a space inside of the gridded structure that suits the size of their group and desired seating position. Low-hanging cantilevers shelter groups of visitors, a modest ledge located towards the top provides a solitary lookout point, and steps at the bottom welcome small crowds and corners, providing a sense of intimacy for one or two visitors. The pavilion’s steady flow of visitors, each inhabiting the space in a slightly different way, highlights the rich spatial diversity that is otherwise camouflaged by the uniformity of the grid.

Fujimoto’s Serpentine Pavilion draws a particular similarity to his 2008 project in Kumamoto, Japan, Final Wooden House. At first glance, these two projects bear little resemblance. From an exterior view, Final Wooden House maintains the crisp outline of a cube with 4.9-meter-long edges, and lumber dominates as the main material in lieu of snow-white steel. In his Sou Fujimoto’s Radical Experiments, Toyo Ito observes that this “cave” is designed simply by hallowing out the interior: “It is no more than the act of reducing a house to its most primitive state by erasing the architectural components.” The interior is truly cave-like, requiring visitors to squeeze through cramped openings in order to maneuver in between irregular stacks of 350-mm-square lumber blocks. Floor, furniture, structure and steps are all one in the same. Similar to the Serpentine Pavilion, it offers a full breadth of spaces to suit a range of activities. Climbing these lumber blocks is akin to the natural practice of jumping in between tree branches and, in that sense, it suits its forest setting just as Serpentine Pavilion’s blurry edges mimic the leafy canopies that surround it.

These seemingly random arrangements of materials that embrace unhindered place-making in order to encourage a “primitive” existence are not determined by chance or whim. The worktables in Fujimoto’s office are piled high with white models that are used in order to test out the seemingly endless variations of interactions between forms. These tables, occupied by interns from all over the globe, are encircled by a single loop of staff desks, which forms the intimate environment in which all of Fujimoto’s current projects (and all of their possible variations) remain on constant display. Fujimoto shuffles between the edges, tweaking minute details until each deadline, with an unparalleled attention to detail. The environment seems to have emerged naturally, and transforms in tune with each new project. Although not a single plant can be found in the raw office space (aside from images of lush greenery pinned to the unfinished walls and tall piles of model trees), it is nevertheless imbued with the atmosphere of a natural setting. This, too, is a cave. Each inhabitant defines his or her own modes of living amid shifting piles of models and images. Recognizing the potential of these modest, simple living environments, Fujimoto masterfully infuses them with beauty, luring his captive audience towards a primitive future.