Starting in 2700 BC and accelerating after 2500, the main urban sites grew considerably in size and were surrounded by towns and villages that fell inside their political sphere of influence. This indicated that the area was home to many political entities. Many sites in Upper Mesopotamia, including Tell Chuera and Tell Beydar, shared a similar layout: a main tell surrounded by a circular lower town. German archaeologist Max von Oppenheim called them "Kranzhügel", or “cup-and-saucer-hills”. Among the important sites of this period are Tell Brak (Nagar), Tell Mozan, Tell Leilan, and Chagar Bazar in the Jezirah and Mari on the middle Euphrates.