The birth of Serdica refers to the mid 1st century AD. It is likely that its foundation was connected with the annexation of the Thracian Kingdom of Rhoimetalkes III in 45 AD. The newly formed Roman province was named Thrace and submitted to the rule of a procurator. The archaeological evidence shows that the original settlement was organized on the Roman model – with a proper layout and streets oriented according to the directions of the world. The buildings were of a wood-earth construction. Serdica probably had the function of a military settlement (castellum).