Perched at the northwest edge of an island in Georgian Bay, the Grotto Sauna is a feat of old-world craftsmanship and new-world sustainability made possible by cutting-edge software and fabrication technology. When the clients—avid architecture and design enthusiasts—commissioned our studio to build a sauna, they wanted “to be surprised” by an out of the ordinary design and part of a creative storytelling process. Inspired by an Italian grotto—a secret and sacred water-filled cave—our experimental design pays homage to the extremities of the landscape to forge an architectural experience. The craggy island, located amongst some of Canada’s most pristine wilderness, posed substantial logistical challenges that required inventive design and sustainability solutions. We enlisted everyone at our studio to pitch design ideas based on digital scans of the site, which allowed optimal orientation of the building with minimal excavation and maximized creative input. Prefabricating the sauna and delivering it to the island significantly reduced the potential time spent on site as well as construction impact on the environment. It was paramount to build a structure that communicated with the unique natural landscape and engender an experience that amplified the salutary effects of a sauna-cum-retreat. To the extent that the clients’ goal was to have the architecture tell a story of escape and refuge, we conceived of a design that married contrasts to transport visitors into an otherworldly sanctum. A simple but dignified exterior built from charred cedar (prepared using the traditional Japanese Shu Sugi Ban method) conveys a weathered appearance—it’s as if the building has been hidden in plain sight for centuries. The warm, curved interior emulates Lake Huron’s waves and mirrors the Precambrian shield—a soft, undulating rock surface that has been worn over billions of years. The luminous glow of the interior wood enhances the sunkissed experience of using the sauna.