Only a few know that it was in the 1930’s that Oia took this name. In ancient times, Oia was the name of the city (“Thireon polis”) where Kamari is today. Apparently, ancient Oia was the port of ancient Thira, the city which was built on the top of Mesa Vouno Mountain, on the south of Santorini. The first name of the current settlement of Oia was Saint Nicolas castle or Epano Meria ( Panomerea) . This is how the village on the north end of the island was named, when Santorini was attached to the Duchy of the Archipelago in 1207.

After the Fourth Crusade and the taking of Constantinople by the Crusaders in 1204, the Republic of Venice chose the Cyclades Archipelago. The Venetians, having sailed around the world, chose the areas with the biggest commercial opportunities. They weren’t interested in agricultural soils, as were the Crusaders, but cared more about their commercial interests. Thus, they asked the Byzantines for the islands of the Aegean Sea, which were important seaways of that time. Marco Sanudo was the first duch, who, in 1207, created the Duchy of the Archipelago. Santorini was handed over from Marco Sanudo to Jacomo Barozzi. The Latin settlers built 5 fortresses, where they settled; the so-called Castelia. Each one had its own administrator. The first castle, the Castle of Saint Nicolas or the Castle of Epano Meria, situated in current Oia, was given to the Dargenta lords, who were Romanised Greeks. The second castle rises in front of current Imerovigli and was the Castle of Skaros. Barozzi, along with his family and other nobles settled there and this castle housed the central Venetian administration. The rest of the castles were in Pyrgos, Emporio and the fifth in the south edge of Santorini, in Akrotiri. In the end of the 13th century, the power belonged to the Western men, who created a social status similar to the one of the West. The Catholics, who started coming to the island after the creation of the Duchy of the Archipelago, were mostly Venetians. With time, though, more people started coming, from other parts besides Venice. They came from Spain, Portugal, France, as well as from Byzantine territories ( Asia Minor, Mainland Greece, Pontos) .

At that time, piracy, as ancient as navigation, was a great plague. Santorini was one of the pirate’s favourite hideout islands. The number of pirate raids was so big that it is mentioned that the population had significantly decreased. So the poor islanders made the decision to build their settlements in higher and more inaccessible areas, where they could be out of sight and thus safe.

They built or carved the rock at steep places. Two-storey or three-storey attached cave houses, with raised exterior walls, so that they would create the walls of the castle and those of the settlement. In some places there were small openings- observation posts, the so-called Goulades.

The Castles of Pyrgos, Emporio and Akrotiri were not destroyed completely by the earthquakes, thus allowing you to see the way they were built. However, that’s not the case in Oia. Today, someone who visits the north-west edge of Oia actually visits the ruins of the castle-observation post. The building had been intact, along with the Curch of Panagia the Platsani, until the catastrophic earthquake of July 1956. The Varozzi family kept Santorini for 128 years (1207-1335) . In the year 1335, the rulers of the Duchy of the Archipelato, the Sanudi attacked them and managed to annex Santorini to their territories. They reinforced their fortifications in all the castles, they favored the wine growing and they launched the cultivation of cotton. The cotton was a different and unique plant. It was perennial and not one-year like in other places (sowing and harvest in the same year) , it lived for more than one hundred years. It was like a low-raised tree, similar to the vineyards. But its uniqueness was its reddish, silky colour. As for the wine of Santorini, it continued being sold at the same markets of the East even after the fall of Constantinople. (1453) . In November 1357, there was a big volcano eruption. Palea Kameni, which once was one island, was divided in two. In 1387, Santorini was handed over to the Crispi Duchy. Finally, in 1566 the Duchy of the Archipelago was handed over to the Ottomans. After 359 years (1207-1566) the Duchy of the Archipelago ceased to exist. In September 1650 occurred the great eruption of the Columbo volcano. This volcano is now underwater. It is located on the north-east side of Oia and is just 6, 5 km from the shore. The eruption was tremendous and lasted over two months, accompanied with strong earthquakes and lava ejecting. On 29th September a seismic sea wave covered a large part of the valley, destroying numerous cultivations. This wave reached the island of Crete. From the lava, a reef was created, and it was given the name Columbo. Its base is 300 meters deep while its top is only 19 meters from the surface of the sea.

The word Columbo is the corruption of the word colomba, that means dove. This volcano, unlike the others, the Palea and Nea Kameni, which are black, is all white, like the dove. This is why, before it sank in the depths of the sea, was named Colombo or Columbo.

During the liberation struggle against the Ottoman Empire (1821) Santorini offered so many ships and crew that was ranked third after the islands of Hydra and Spetses.

On 5th May 1821, anniversary of Saint Irene, the delegate of D. Ipsilantis raised the flag of Revolution on the island of Santorini. After Greece was liberated, Santorini became a province of the new Greek nation (1827) .