A singular opportunity to create a significant Wine Country estate on one of Sonoma's most coveted addresses. Set on approximately 4.44 acres midway along Castle Road, the property offers rare scale, privacy, and proximity to Sonoma Plaza in an irreplaceable Eastside setting. Castle Road is uniquely defined by its blend of larger estate properties, quiet Wine Country character, and exceptional proximity to town, with the road culminating at Bartholomew Park & Winery. The property is offered with an extensive body of planning and design work already completed, including full construction plans by Sutro Architects for a proposed estate encompassing approximately 10,000 square feet of conditioned space across a main residence, guest house, second dwelling unit, and pool house. The vision also includes a pool, tennis or sport court, agricultural pasture and barn, and thoughtfully considered landscape plans. Approved six bedroom septic designs, well and infrastructure planning, arborist work, archaeological study, topographic mapping, vendor information, reports, and the status of permit applications will convey with the sale. A remarkable opportunity to carry forward an established architectural vision or use the extensive work completed to date as the foundation for an entirely personal Sonoma estate. Rare acreage, exceptional proximity, and one of the most historic, coveted addresses in Sonoma.