The group of the cities of Meda'in, the administrative capital of the Sassanid Empire from the early Middle Ages to the collapse of this empire, is one of the biggest metropolises of the antiquity and of the Middle Ages. The group of the cities of Meda'in, consisting of many cities and towns built in different sizes and various times, has a diverse demographic mosaic. This group of the cities, built on the bank of Tigris, at a point where Tigris and Euphrates are very close, is an important economic centre due to its agricultural and commercial intensity, and also has a modern city appearance with the traces of the different cultures due to its palaces, mansions, and various architectural style. This group of the cities, having been capital to the many empires in Mesopotamia, had become the heart of the Middle East thanks to its politic and administrative importance. This group of cities, a junction point of the routes between East and West, could preserve its importance until the Abbasid Period, but lost its dynamics after the establishment of Baghdad by the Abbasids in the same period.