[2] The municipal unit includes the uninhabited islands Gyaros (lying to the northwest of Syros) and Varvaroúsa.

It is a classical cycladic medieval settlement that is densely built with narrow roads, circular order and a radial street plan.

Frankokratia ended during the 16th century but the Catholics of Syros came under French protection and Catholicism survived in the island.

Nevertheless, the settlement remained a religious centre since it is the seat of Roman Catholic Diocese of Syros and Milos.

Many Catholic inhabitants of Ano Syros (and someone from Tino) were later imprisoned by the Greeks (Orthodox) with the charge of collaborationism in 1945.