The Randstad and polycentric regions generally are not only vehicles to create critical economic mass. The geography of the Randstad is unmistakably deltaic, with expanses of flat open land crisscrossed by watercourses and historic windmills that remain from a former network of more than 10,000. The development of extensive physical and soft infrastructure has since the seventeenth century gone hand in hand with the growth of the economy and international trade. In 2017 the Randstad was the fourth largest metropolitan economy in Europe, after London, Paris, and the Rhine-Ruhr (also polycentric), and before the COVID-19 crisis was experiencing reasonably good growth throughout the later 2010s of about 2.5% per year. The idea of the Randstad as a polycentric metropolis is a consistent feature in the modern history of Dutch spatial development and planning, but there have been many twists and turns. This chapter also presents an overview on the key concepts discussed in this book.