 It remains a titular see of the Patriarchate of Constantinople as well as being, since the mid-15th century, a titular archbishopric of the Roman Catholic Church.Nicaea was an important and prosperous city in Late Antiquity, and its local church flourished as a result.The First Ecumenical Council was held in the city in 325, and under Emperor Valens (r. 364–378), the local see was removed from the purview of its neighbour and rival, Nicomedia, and raised to the status of a separate metropolis.