roman books such as the periplus of the erythraean sea and ptolomey's "geography" list a string of market places (emporia) along this coast. finds of roman-era coins along the coast confirm the existence of this huge trade even in coastal tanzania, and ptolomey's geography refers to a town of rhapta as "metropolis" of a political entity called azania near actual zanzibar. archaeologists have not yet succeeded in identifying the location of rhapta, though many believe it lies deeply buried in the silt of the delta of the rufiji river.