The work synthesises in 26 monographic chapters the results of a six-years long (2012 – 2018) interdisciplinary international project whose aim was to present the state of knowledge on today’s Poland during the Migration Period, and to compare the evolution of its settlement with that of its neighbours. One of its main results – the accordance between the palynological evidence of the change of environment (extensive reforestation and drastic reduction of anthropogenic indicators) and the archaeological reconstruction of the change of settlement (disappearance of the Przeworsk, Wielbark and other cultures of the Roman Period by the mid-fifth century) – conclusively confirms the often questioned verdict of a sudden severe depopulation of the lands between the Vistula and the Oder, similar to that revealed in the rest of Central/Eastern Europe (disappearance of the Elbe and Chernyakhiv-Sântana de Mureş cultures). An entirely new perspective opened by the project is the survival of enclaves with contacts all round the compass (the Eastern Empire, the Merovingian West, the Danubian lands, Scandinavia, the Western Balts). None of them yielded Slavonic material, even the longest-lived one recently discovered at Gąski-Wierzbiczany in Kujawy, evidently one of the main centres of the European Barbaricum and in the third and fourth century the Roman army’s recruiting station, which continued till the early seventh century; this evidence (or lack of it) is the death-blow to the theory of a supposed continuity of settlement – and so of ethnicity, necessarily Slavonic – from the Bronze Age to the Middle Ages. Through these enclaves, southern cultural influences reached Scandinavia during the Younger Germanic Iron Age; the one at the mouth of the Vistula seems to have been the earliest and greatest recipient of the Imperial solidi in the Baltic zone, from which they were redistributed to the Nordic lands. A sample of other topics: tracing the extent (quite limited) of the Hunnic presence north of the Carpathians; evidence on fugitives from Hermanaric’s realm, including what appears to be the earliest known assemblage of the Dančeny-Brangstrup horizon; the Migration Period among the Western Balts, neighbours and cultural cousins, who did not take part in the Völkerwanderung. In the end, two leitmotifs of the work, one pessimistic, the other optimistic: short-sightedness and harmfulness of the official persecutive policy, in Poland and the majority of other European countries, with regard to amateur metal detecting, which only makes priceless potential evidence disappear without a trace; material remains and relative written sources (in this case Iordanes and Procopius) reflect the same historical reality and can legitimately be used to support one another.