The largest patterns of human genetic variation within the Netherlands show strong correlations with geography and distinguish between: (1) North and South; (2) East and West; and (3) the middle-band and the rest of the country.
The largest genetic differences within the Netherlands are observed between the North and the South (with the three major rivers - Rijn, Waal, Maas - as a border), with the Randstad showing a mixture of these two ancestral backgrounds.