The Gion Kobu Kaburenjo theater is where Kyoto's geisha and maiko perform Miyako Odori group dances. The Yasaka Kaikan was built next door for theatrical performances. The building skillfully incorporates Japanese architectural concepts including a multi-tiered roof and tower-like facade. Obayashi Corporation's Tokusaburo Kimura, a renowned master of theatrical architecture in his day, designed the original structure, and Obayashi Corporation constructed the building.

A decision was made to transform the building into a hotel with a structure that complied with the current Building Standards Act of Japan while preserving the historically significant exterior. Discussions on exactly how to achieve that aim went on for several years in various forums, including the committee on the preservation and utilization of the Yasaka Kaikan.

Reflecting on that process, the committee member responsible for architectural design, Naoyuki Ito, points out that "the building serves as a landmark for generations, so we needed to develop a solid evidence-based approach for each aspect of the project. I learned a great deal from listening to the exhaustive exchange of opinions among people from a wide range of backgrounds."

The biggest constraint was building height. Any new buildings constructed in the Yasaka Kaikan area were not supposed to exceed 12 m in height. However, Obayashi was able to maintain the original 31.5 m height by making use of the special exceptions for a building with excellent form and design or a building that improves the townscape, and the project became the first in Kyoto City to exceed the current height limit.

Following repeated landscape discussions and review board meetings, Kyoto City finally approved the design, which sought to retain the exterior walls and structural frame on the south and west sides, and to preserve the original Yasaka Kaikan silhouette on the north and east sides so the new building would meld perfectly into the traditional Gion townscape.

Despite having encountered multiple challenges along the way, everyone is driven by a unique sense of fulfilment at being involved in a major project linking the past, present, and future. According to Ito, "There were times when we felt like we were conversing through the drawings with the great Tokusaburo Kimura, a long-ago member of the design department. And it is very moving to imagine that, many years after completion of this newly regenerated building, another generation of Obayashi designers might work on it."

Structural architect Akihito Fujii describes the Imperial Hotel Kyoto project as perhaps the most challenging project of his 35-plus-year career as a structural engineer. Despite the wealth of reference materials that remained, during the process of demolition, discrepancies emerged in some areas between the drawings and the actual building due to its age.

For instance, some columns were actually thicker than expected and the positions of some rebars were different. If there was any doubt, designers and on-site personnel would work together closely to determine the best construction method. "Once the demolition work got underway, we conducted chipping tests to determine the main reinforcement positions for all columns, renewed the design accordingly, and resubmitted the building confirmation application," explains Ito.

"I really admired the amazing on-site work, particularly with regard to the complex reinforcement, for which there was no precedent. We always responded to any frontline queries as quickly as possible to avoid halting the works."

Given the risk of collapse in the event of a major earthquake, it wasn't possible to dismantle the building all at once and just leave behind the two walls and partial structure earmarked for preservation. Consequently, even the planning of temporary works during construction had to be led by the structural architects. Such work more than doubled the amount of time and effort required compared to a regular demolition and new construction project of a similar size.