The villages of Butmir, Lengyel, Jablanica, and others in southeastern Europe show us a condition of advanced culture here also.[44] Déchelette, speaking of the culture of this region, notices "the striking analogies between these old walled villages of the Balkans and the Danube valley, and those of the Ægean villages of the Troad and Phrygia." Primitive idols, painted pottery, frequent use of the spiral in decorative art, all these reappear here and there in the Neolithic stations of southeastern Europe, and in the eastern basin of the Mediterranean in pre-Mycenæan and Mycenæan days. Evidently houses, settlements, modes of life, and stages of culture differ greatly during the same epoch of the Neolithic period in different parts of Europe. Italy was always far in advance of Europe north of the Alps. But even in northern Europe there was great diversity. Shell-heap dwellers still remained long after a much higher culture prevailed throughout most of Denmark. The life and thought of the pioneer hunters of northern Germany, and still more of northern Russia, were very different from those of the agriculturists along the valley of the Danube and in the Balkan Peninsula. In Greece little city-states began to arise early. Even in northern Europe density of population and size of settlements varied greatly. One illustration of these differences can be seen in the occurrence of fortified villages and refuges.[45] The age of these fortifications is as great a problem as that of the remains found in a pit-dwelling. The village may be, probably usually is, much older than the surrounding wall, and an earthen wall may contain Neolithic or even perhaps Paleolithic implements. The custom of fortifying villages evidently spread rapidly during the Bronze and Iron periods. Sophus Müller tells us that all walled settlements north of the Alps are far younger than the Neolithic period.[46] This statement, often disputed or neglected, is probably an exaggeration, but may well be true of the region surrounding the Baltic. The sparse and scattered hunting and pioneer population of Scandinavia and Germany had no need of building permanent walls around their single houses or small villages. They had very little wealth to protect. But an agricultural population inhabiting a fertile region open to attack might well surround their villages with a wall, or provide a burg, or fortified place or "refuge," whither they might drive their cattle or transport their grain. Examples of this are Stutzheim and Urmitz, in the Rhine valley, always a great thoroughfare, and in Switzerland and along the maritime Alps villages of this sort seem to have been fairly frequent. Apparently they were still more numerous in the valley of the Danube and in the Balkan Peninsula. It is not at all surprising to find them in Thessaly, so near to the advanced civilization of Greece.