The renowned Kuma, whose work embodies Japanese sensibilities with a modernist veneer, is well-known for integrating architecture with nature—as his design for the Nezu Art Museum in central Tokyo illustrates. So, it only seems fitting that the prolific architect was sought after when the Portland Japanese Garden was looking to expand.

Nestled in an urban forest surrounded by a residential neighborhood in the hills of Portland, Oregon, the Portland Japanese Garden is a beloved cultural attraction that was starting to outgrow itself. The garden—which is often referred to as the most authentic Japanese garden outside of Japan—was designed by Professor Takuma Tono of Tokyo Agricultural University in 1961. However, a sharp increase in visitor attendance, combined with the site's limited footprint, was threatening the zen-like peace and tranquility that's integral to the experience. With their sights set on Kuma for the expansion, CEO Steven Bloom and the board members wondered how “a little Japanese garden in the hills of Portland” would be able to woo this world-class Japanese architect. As it turns out, all they had to do was invite him to visit, and the project sold itself.

Plans for the expansion included equal parts architecture and landscaping. Kuma referenced Kyoto's Katsura Rikyu, a traditional masterpiece of Japanese gardening, as he “adjusted the Japanese spirit to Portland's landscape." Collaborating together with Sadafumi Uchiyama—a third generation Japanese gardener from Kyushu who is the Garden Curator—the existing land was reused and optimized, adding an additional 3.4 acres of space to the 9.1-acre garden to create an adjacent Cultural Village. The concept of a "village" outside the "gate" is nothing new, as it emulates the traditional monzen-machi, or "temple-towns" that surround sacred shrines and temples in Japan.

Set around a south-facing courtyard that overlooks the original garden, the structures that make up the Cultural Village include a "Village House," "Garden House," and a "Tea House." The buildings are laid out in a zig-zag sequence using a traditional method called "Gancho" planning, which refers to the pattern of flying geese. At the west end of the plaza features a "Castle Wall," which was constructed with traditional Japanese hand tools and techniques by Suminori Awata, a 15th-generation Japanese master stone mason who was flown in to work on the project.

The expansion earned LEED Gold-certification. However, in addition to some of the usual suspects like high-efficiency lighting and fixtures, many of these green elements will never be seen by visitors. Taking advantage of the moderate temperatures in the ground, 24 geothermal wells were added 300 feet down beneath the Cultural Village Plaza. The geothermal wells boost energy efficiency and reduces the operational costs of heating and cooling the buildings.

Another green addition is the use of living roofs on all the structures. The green roofs act as Kuma's translation of the traditional Japanese thatched roof. Each one was set with sedum on special tiles called “greenbiz," which were invented in Japan by Komatsu Seiren Co., Ltd. The porous tiles absorb some of the rain water—as does the sedum—while the excess water drains into the system.

Below the parking lot lies another hidden gem. To ease pressure put on the city's sewer system, Garden Curator Uchiyama designed a unique system to channel the by-rain water runoff. A stone creek was added to run from the top to the bottom of the hill. Dry in the summer, the creek will channel the runoff during the rainy season from the upper to the lower Garden areas. The water will go into the hidden holding tank under the parking lot, where it will be slowly released into the city's sewer system. This state-of-the-art water management system also helps alleviate the risk for landslides.

PURE + FREEFORM designed and manufactured the metal panels used on the facade and pitched roofs. They worked with Kuma to design a custom-aluminum finish specifically for the project that they call Celeste Stone. The final result features a silver-and-white pearl detailing and a matte-granite layer on top.

With so many unique elements in this cross-cultural expansion project, Kuma's thoughts on his favorite certainly evoked the original zen spirit he sought to maintain. "I think guests will enjoy the space between the buildings. The buildings, of course, are important, but the space between are sometimes more important than the buildings themselves," he says.