During the early Middle Ages, Slavic tribesmen inhabiting what is now the Czech Republic used to bury their dead under barrows. This practice has been widespread in southern and eastern Bohemia and some neighbouring regions, like Upper Austria and Lusatia, which at that time have been also populated with Slavic people. There are no known Slavic barrows in the central part of the country (around Prague), nor are they found in Moravia. This has led some of the archaeologists to speculations about at least three distinct waves of Slavic settlers, who colonized Czech lands separately from each other, each wave bringing its customs with it (including burial rituals).