Rare single-level mid-century modern designed by noted architect Robert Klemmedson, thoughtfully positioned on an expansive approximately half-acre corner lot to capture exceptional natural light, seamless indoor-outdoor living, and views of Mt. Diablo and Orinda Country Club. Walls of glass span the rear of this updated residence, filling the home with natural light and framing the surrounding landscape. 100 El Toyonal offers 4 bedrooms plus an office (possible 5th bedroom), along with a bonus room off the bedroom wing overlooking the patio and views beyond. The living room, dining room, breakfast nook, and primary suite are all oriented toward the expansive patio, deck, and outdoor setting, creating a strong connection between the interior living spaces and the natural surroundings. Updated kitchen and bathrooms blend refined modern finishes with the home's original architectural character, complemented by all new custom double-pane windows and sliding doors. The lower yard offers a pool, expansive usable outdoor space, and a well, creating a rare opportunity for future customization and development. Whether envisioning an ADU, SB9 lot split, sport court, gardens, outdoor entertaining spaces, or additional amenities, the possibilities are extensive (buyer to verify). Additional features include a flexible bonus space off the family room, a spacious attached two-car garage with work area and storage, and an antique underground bomb shelter that may offer potential for a wine cellar or additional storage. Ideally located moments from Orinda Park Pool, downtown Orinda, BART, bus lines, top-rated Orinda schools, and freeway access, 100 El Toyonal presents a rare combination of exceptional mid-century architecture, dramatic views, architectural integrity, and exceptional future potential in a highly desirable close-in Orinda location.