This article is an archaeological report on the results of the excavation carried out around the fi lled-up river branch and bridge No. 1 in Mikulčice in 2012 (excavation B 2012). The main aim of the research was to complete the fi eld works at bridge No. 1, which was discovered during the large-scale excavations performed at the defunct river channel in front of the NW gate of the bailey in 1966-1968. At the same time, the question of how the river channel developed at the site of the bridge was investigated, as well as the topic of the settlement in the wider area between the bailey and the north-western suburb. Presented along with the interpretation of the movable fi nds from the defunct river branch were two possible variants on how the settlement developed in relation to the gradual fi lling-up of the river channel. After analysing the fi nd circumstances in area B 2012, the authors inclined towards the second variant and thus revised the existing theories concerning the evolution of sedimentation in the area of the extinct riverbed. This has helped to resolve some key questions regarding the existence and demise of the power centre in Mikulčice., Marek Hladík, Lumír Poláček., and Obsahuje seznam literatury