The Mill is one of the oldest industrial buildings in Poland. It was built on the left-bank of the Słupsk next to the bridge upon the Młynówka, on the Duke’s estate, around 1310. The mill was propelled by the water wheel installed on the canal dug from the direction of the Słupia. The amount of water in the canal was regulated by water gates. The large volume of the mill for that time, and its small narrow windows preserved in parts of the ground floor of the Gothic walls, suggest that the building was also a granary.

On the three levels of the mill-granary, a permanent ethnographical exhibition was organised depicting the folk culture of Central Pomerania. The exhibition covers the culture of the indigenous population (the Slovincians, the Bytów Kashubians, the Złotów Krajna people, and also residents of Jamno and Łabusz – villages near Koszalin), and also the folk cultures of the settlers who came to Central Pomerania after the last war.