The summary provides an overview of the essays collected in this volume and places them in the context of research that has innovatively redefined the theme of the “frontier” in the Early Middle Ages in recent decades. In doing so, it shows how the concept of border is used in the essays not only in its political, but also in its ideological and cultural sense. Despite the diversity of perspectives and themes, however, a common feature emerges: the prevalence of “porous” and “blurred” borders that testify to a dynamic political and cultural reality that is constantly being redefined.