Extensive surveys in the Niger Delta have revealed a series of massive, circular platforms paved entirely with millions of crushed oyster shells. These structures, dating back to approximately 500 CE, are located at the confluence of several major river branches and show signs of heavy acoustic resonance, indicating they were used as communal dance floors for large-scale rhythmic ceremonies.
Archaeologists from the University of Ibadan believe these sites hosted the "Festival of the Mangrove Spirit," an event that celebrated the harvest of coastal resources and the seasonal change in water salinity. The persistence of similar shell-mound traditions in modern coastal Nigerian cultures suggests a deep, unbroken heritage of maritime festivals that has survived for over fifteen centuries.