San Francisco–based Aidlin Darling Design crafted the program of this private spa retreat, located in the mountains of Sonoma, Calif., to serve as a place of respite, with the structure sited within a grove of oak, manzanita and madrone trees, close enough to the main house so as to be convenient, but far enough to ensure privacy on the 10-acre site.
The entry is situated behind two curving earthen walls that make the approach somewhat like moving through a concrete Richard Serra sculpture. Inside, the 1,802-square-foot structure includes a yoga and meditation studio, a steam room, changing rooms, and a refreshment bar. The spaces are organized on a wood deck surface that projects out over the landscape to the northeast and southeast to provide a private sundeck, which is shaded by a slatted canopy. Retractable glass walls open the interior spaces to the outdoors.