409 21st St Set in the esteemed North of Montana neighborhood of Santa Monica on a nearly 9, 000 SF oversized lot, this custom-built new construction blends quality craftsmanship with exceptional amenities and scale. Spanning 6, 860 SF with 4 bedrooms + office and 7 bathrooms across three levels, this home delivers seamless indoor-outdoor flow and expansive spaces built for elevated living and entertaining. The main level offers soaring ceilings and expansive living spaces, including a formal living room, dining room, dedicated office, and an open-concept kitchen outfitted with bespoke cabinetry, butler's pantry, and Miele, Sub-Zero, and Wolf appliances. Large folding glass doors connect the interiors to a private backyard retreat featuring a heated pool and spa with automatic cover, a built-in BBQ and pizza oven, and multiple zones for dining and lounging. Upstairs, wide-plank oak flooring leads to three generously sized en-suite bedrooms, including a reimagined primary suite with a newly expanded oversized walk-in closet. The amenity-rich basement level includes a lounge and bar, movie theater, wine cellar, guest suite, and full spa with both wet and dry saunas. Mature ficus trees line the front of the home for added privacy and additional highlights include solar panels, multi-zone climate control, Control4 smart home system, and a three-car garage. Located just moments from Montana Avenue, San Vicente, and Brentwood Country Club, this home offers a rare opportunity to enjoy scale, privacy, and convenience in one of the Westside's most sought-after neighborhoods.