タカトタマガミデザインが長野県で手掛けた、童話の風景を立ち上げたような〈SORA stairway（SORAへ登る螺旋階段）〉

Elevation: 1,770 meters. This observation tower is located in the summit area of Ryuo Mountain Resort.

Ryuo Mountain Resort, where this facility is located, was originally operated as a ski resort. Still, in recent years, efforts have been underway to transform the resort with a focus on off-season utilization. In particular, to capitalize on the site’s unique location at the summit—which offers a 60% chance of seeing a sea of clouds—efforts have been underway to enhance visitor appeal during spring and summer, including the development of an observation terrace and the renovation of the restaurant. Takato Tamagami Design was responsible for the design of these facilities, and this project was also entrusted to them, as the facilities were intended to serve as the core of a new visitor attraction.

Initially, plans called for an observation bridge cantilevered out over a steep slope, and the project had progressed as far as rendering proposals. However, through repeated discussions with the client and on-site surveys, the team concluded that the observation facility should not be viewed merely as a vantage point, but rather as a compositional element of the landscape against the backdrop of the sea of clouds. By erecting a tall structure slightly below the viewing platform, it would become a landmark appearing as a silhouette in the distant landscape, while simultaneously creating the experience of “climbing” itself. Thus, the plan shifted toward a tower-like observation facility that rises as if to touch the sky.

The tower’s primary structure consists of a staircase spiraling around a central support column. The form is an abstraction of vines缠绕ing a tree, and the goal was to create an observation tower with a narrative quality that instinctively makes people want to climb it. The spiral’s diameter is not uniform; it varies with location. This creates an organic, dynamic exterior while also introducing spatial variations throughout the ascent.

The approach from the entrance to the central pillar is designed to traverse a steep elevation difference via a retaining wall, giving it the appearance of a bridge. Here, visitors experience the boundary where they are separated from the familiar ground of everyday life and transition into the extraordinary. Next, climbing the spiral-shaped steps attached to the pillar creates a temporary sense of stability. As one ascends further, the treads disappear, and the spiral path gradually widens. As the stairs move away from the support pillars, the transparency beneath one’s feet increases, guiding visitors to the very top amid a sense of floating and tension.

The top step is a semicircular landing offering panoramic views of the sky and mountain ranges in all directions. Under the right conditions, visitors experience the sensation of standing atop a sea of clouds, surrendering their bodies to the ever-changing landscape.

The harsh site conditions at the 1,770-meter summit imposed significant constraints on both the design and construction plans. The only means of access to the site was a ropeway. Although it was one of the world’s largest, with a capacity of 166 passengers, it was subject to restrictions limiting the load capacity to approximately 10 metric tons and the suspension length to 7 meters. The only heavy equipment available at the summit was a hydraulic excavator left behind during the construction of the summit station, and it was impossible to bring in any new heavy machinery. Consequently, it was necessary to divide and lighten the structural members so that they could be transported by hand.

Furthermore, while scaffolding was essential for assembling the 14.5-meter-tall tower primarily by hand, the site was on a steep slope. Therefore, it was first necessary to create a level working area for scaffolding installation, and construction began with earth-cutting and retaining wall work. Since work would be suspended during the winter due to snowfall, the project spanned two seasons: site preparation in 2024 and main construction in 2025.

From the planning stage, it was anticipated that the number of components would be quite substantial. It was determined that if all of these were bolted together, the structure might appear too clunky against the natural landscape; therefore, on-site welding was adopted as the primary joining method. Consequently, a steel fabrication and construction company with expertise in on-site welding was selected from the outset. A team was formed with contractors familiar with the local environment, and the design was developed through repeated consultations involving the structural engineers.

As a result, despite the challenging construction conditions, a surprisingly elegant form was achieved. The completed observation tower exhibits such high precision that it is hard to believe it was assembled on-site from approximately 1,500 individual components. This is entirely due to the construction team’s high technical skill.
(Takato Tamagami)

Location: 11700 Yomase, Yamanouchi-machi, Shimotakai-gun, Nagano, Japan
Principal use: Observation tower
Client: Kitashiga Ryuoo
Completion: 2025

Architects: TAKATO TAMAGAMI ARCHITECTURAL DESIGN
Design team: Takato Tamagami, Nanami Yamakawa
Structural engineer: Munehiro Minagawa / Ji-mune Structure and space Laboratry
Construction: Yumoto Construction, MATELIER

Photographs: Masaya Yoshimura

Construction type: New Building
Main structure: S
Design term: 2023.06-2025.03
Construction term: 2024.04-2025.07