The development of the sub-areas of metropolitan regions is heterogeneous. Although the core cities can count on further population growth, the intermediate centers in particular have to adapt to further changes in growth. The article describes the location of medium-sized centers between metropolitan regions and their importance as a driving force for demographic and economic growth. Accessibility potentials are calculated on the basis of locations in the northern German metropolitan regions of Hamburg, Nordwest (Bremen-Oldenburg), and Hannover-Braunschweig-Göttingen-Wolfsburg, in order to describe the relative centrality of medium-sized centers. Sometimes, the medium-sized centers are more central than the metropolitan regions themselves and contribute to the stabilization of regional development in the spaces. Three conclusions can be drawn from this observation: first, that concentration processes can occur within rural communities and towns; second, that there is a need for flexibility in the concept of central places; and third, that spatial planning in cooperation with regional policy plays an important role in strengthening these centers.