DWIN. — A city also called “Ostan” by Armenian historians, because COSROE II transferred his court there in the 3rd century. Within its walls, in 478, the see of the Armenian katholikos was transferred, remaining there until 931. Many synods were held in Dwin, four of which remained famous: the first under the katholikos Nerses II in 554–55, which also established the Armenian era; the second under Moses II, against Cyrus, metropolitan of Georgia; the third under Nerses III; the fourth under John of Otzun in 719–20, against the Paulicians and Messalians. It was several times destroyed by the Arabs; its last complete destruction is attributed to a terrible earthquake in the 13th century.
Enciclopedia Cattolica