THE CONE 軽井沢の逆円錐














Inverted- conical roof makes soft boundary for life

This is a plan for a timeshare villa in Karuizawa. It is positioned as an entity that falls between a hotel and a residential home, requiring added value that appeals to many people.

The site is approximately 3,000 square meters, mostly steeply sloped while also featuring rich forests. The floor plan has been designed to follow the shape of the slope, taking the form of a segment of a circle. By rotating a sloped cross-section that opens up to the forest along this plan, the roof naturally forms part of an inverted cone.

The structure is legally classified as wooden. However, to achieve a large span of 15 meters by 12 meters in the living area, the beams have been reinforced with steel. Instead of traditional wooden columns, solid iron columns have been used to minimize column size, realizing a large opening that opens up to the transparent forest. This has resulted in the creation of a neutral architecture without particularly emphasizing the structural type.

This neutrality is most evident in the interior space. To utilize the softness of the inverted cone inside as well, the ceiling has been painted white to act as a large reflector. During the day, it is possible to spend time in natural light alone, and at night, the space is warmly illuminated by the reflected light from indirect lighting.

The corridor on the arc that runs through the center of the building creates a sense of anticipation as its entire form is not visible. Centered around this corridor, spaces of various sizes unfold, providing a rich spatial experience that incorporates the natural landscape of Karuizawa in various ways.

In the living and dining area, the goal was to create a space where humans can feel at ease, even within a large space. Therefore, a fireplace made from a 3-ton boulder found in the mountains of Karuizawa has been placed. This introduces an element of randomness that is beyond human control, providing a sense of place.

This symbolic roofed architecture has brought an interesting aspect of being conspicuously present amidst the rich natural setting.

View from Kitchen to Living Dinig area
1st Floor
Mt.Asama and the roof
Watergarden and the roof
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono
photo: nanako ono


Vortex Co., Ltd.


Site Area 3200m2
Indoor Area 309.8m2
Terrace Area 95.1 m2


Wood with steel reinforcing + Concrete Basement Floor

Partner in Charge/ Design Lead

Shuhei Kamiya

Project team

M.Ogawa, S.Sawai, S. Miyauchi


Noriaki Yamada Structure

Electricity 電気設計




Landscape Design and Construction



Takenami Kenetsu

Project Management

X platform


Takumi ota exept for ones with noteTakumi ota exept for ones with note