De Rat — "the rat" in old Dutch — is a restored 17th-century smock mill in IJlst, brought up from the Zaanstreek and rebuilt here in the 19th century. It is the last working sawmill of its kind in Friesland and one of only a handful left in the Netherlands.
Volunteers run the mill on Saturday afternoons in summer; you can watch them turn the cap into the wind and saw planks the way Dutch shipbuilders did for centuries. The interior is open to visitors when the mill is operating. A few euros' donation goes towards maintenance.