The Three Koornbloem was originally one of a group of 19 mills in Old Schiedam. It was first used as a ’raw’ mill, to process limestone. The mill was built in 1770 by a group of 18 people, who each had a number of shares in the mill. Fifty years later, it was converted to a corn mill. Today, the mill is owned by Schiedam County, and is open to the public. Guided tours of the mill are available by appointment only.