After the gradual disintegration and fall of the West-Roman empire in the 5th century and the devastation by the invasions of Huns, Germanic peoples, Byzantines, Moors, Magyars, and Normans in the next five centuries, little remained of urban culture in western and central Europe.Initially, urban culture recovered particularly in existing settlements, often in remnants of Roman towns and cities, but later on, ever more towns were created anew. Meanwhile, the population of western Europe increased rapidly and the utilised agricultural area grew with it. Urban development in the early Middle Ages, characteristically focused on a fortress, a fortified abbey, or a (sometimes abandoned) Roman nucleus, occurred "like the annular rings of a tree", whether in an extended village or the centre of a larger city". Since the new centre was often on high, defensible ground, the city plan took on an organic character, following the irregularities of elevation contours like the shapes that result from agricultural terracing.In the 9th to 14th centuries, many hundreds of new towns were built in Europe, and many others were enlarged with newly planned extensions. The foundation of monasteries, most of them of the Benedictine Order, also provided nuclei around which traders and craftsmen settled.