“Unquestionably the best building of the kind in Upper Canada” – Statistical Account of Upper Canada, 1817 The Old Stone Mill, the only stone gristmill in Canada designated a National Historic Site, is one of the oldest surviving automatic gristmills in Ontario. Owned and operated by the Delta Mill Society, a non-profit and charitable organization, the Old Stone Mill National Historic Site features interactive exhibits, programs and guided tours that explore the rich history and technology of this 1810 stone landmark. Open daily between Victoria Day weekend and Labour Day, 10 am to 5pm. Other times by appointment. Located on the Rideau Heritage Route.