Opi is a community in Enugu State of South-Eastern Nigeria. It is populated by the Igbo people and located in Nsukka region. It is the location of a prehistoric archaeological site which contains iron smelting furnaces and slag dated to 750 BC. . Iron ore was smelted in natural draft furnaces and molten slag was drained through shallow conduits to collecting pits forming huge slag blocks weighing up to 47 kg. The operating temperatures are estimated to have varied between 1,155 and 1,450 °C.