Welcome to 26 Circle Avenue, one of Mill Valley's most recognized and beloved homes. Long known among locals as the castle house, this remarkable property occupies a rare street to street lot stretching from Circle Avenue to Oakdale, right where Buena Vista meets Oakdale in one of the town's most desirable pockets. This legal duplex offers exceptional flexibility, with 5 bedrooms and 3 bathrooms spread across more than 3,100 square feet of living space. Whether used as a multi-generational residence, an income-producing investment, or a spacious owner-occupied retreat, the layout provides options that are increasingly hard to find in Mill Valley's tightly held market. Cared for by the same family for decades, the home carries a warmth and character that only comes with time. Its distinctive architecture and enduring presence have made it a true neighborhood landmark, and it now presents a rare opportunity for a new owner to bring their own vision to a property with unmatched history. Just blocks from Downtown Mill Valley, Boyle Park, Mill Valley Golf Course and hiking trails, 26 Circle Avenue places shops, restaurants, and open space all within easy reach. Few properties offer this combination of privacy, walkability, and access to everything that makes Mill Valley special. 26 CircleAvenue is more than a home. It is a piece of Mill Valley's fabric, ready for its next chapter.