The Black Poplar, also known as Poplar Mill, is a watermill located in Walden in the District of Vöhren. It is owned by the Walda family and features three water wheels. Two of the wheels are connected to the main building and are used for sawing and operating an oil mill. The third wheel, located in a separate building on the opposite side of the water, powers the flour mill. The wheels are driven by water from the river Holle.   The mill in the Vöhren district is utilized by many residents from surrounding areas. In addition to serving as a mill, its central location makes it a valuable meeting place.