Exomvourgo is not the highest mountain on the island—that is Tsiknias—but is in a central location ringed by many small villages such as Tripotamos and Falatados and can be climbed from several of these.

[7] Under Byzantine rule a fortress, later named by the Venetians Castello di Santa Elena after a chapel on the summit, was built on the mountain and Exomvourgo functioned as the island's capital.

In this era the town inside the castle had a population of 1000-2000 and contained 677 houses, 5 churches and some storage areas and reservoirs.

[8] In 1570 a force of 8,000 Ottoman troops and several cannons, commanded by Canum Pasha, besieged the mountain, but were successfully repulsed.

[12] The Venetians remained in charge until 1715 during the last Ottoman–Venetian war when, long after the rest of the Cyclades had fallen to the Turks, it was besieged by a Turkish force of 65 warships and 74 transports carrying 25,000 soldiers.

[12] The commander and his officers were accused of "treason after bribery" by the Venetian Republic and sentenced to death by swallowing liquid silver[13]/having liquid silver poured on their bodies[12] Bernardo Balbi the rector (governor) of the island, was transferred to Venice and sentenced to life imprisonment for cowardice.