The oldest church of Santorini island is Panagia Episkopi, a former bishop's church from the Middle Byzantine period.
Located at Mesa Gonia on the foot of the mountain, Profitis Ilias, it is dedicated to Virgin Mary, it was founded at the end of the 11th century by the Emperor Alexios I Comnenos.
It is an inscribed-cross, four-columned church with a dome. Preserved in the interior are wall paintings of excellent quality and a wooden, carved templon (iconostasis), decorated in the technique of mastic wax.
There are two stories to why it was built at the end of the 11th century. The first says that an icon of Panagia repeatedly moved from its place on a hillside chapel close by to appear again in a different place. The locals understood this as a sign to build a new church for the icon.
Another legend says that the Emperor Alexius I Komnenos was the donator of the church because he passed by on the entire countryside outside the villages of Gonia and Pyrgos to the church. After a traditional, almost completely destroyed inscription, the church replaced the predecessor of a three-aisled early Byzantine basilica at the end of the 11th and the beginning of the 12th century.
Since 1207, there is a recorded history of this significant and historical church. The Venetians expelled the Orthodox bishop off the island and appointed a Latin bishop. The church was called Panagia Episkopi, as the seat of the expelled Orthodox bishop, while his Latin successor took his seat at Skaros Rock on the cliffs of the caldera.
Next, to the Orthodox altar at the Panagia Episkopi, a Catholic one was built.
The next conqueror was the Ottoman Empire in 1537, where the island, as well as the whole Aegean, was taken over. After that, the Orthodox bishop returned to Santorini and accepted the church again as his episcopal seat. The Catholics did not accept this, mainly because of the valuable property of the church and the income from it. The dispute escalated until 1614 when the church’s lands were shared and both denominations were allowed to hold their services in the church.
The church is considered the best example of the traditional ecclesiastical architecture of the island.
On the walls of the interiors, various icon stands are lined up. The most famous icon that remained in the church is that of Panagia Glykofilousa, which is kept in a special glass case under controlled conditions on the south side of the central church space. The 12th-century portrait is considered the most valuable icon of the church as it refers to Mary as "Sweet Kissing Madonna." The icon shows her embracing Jesus, who caresses her chin.
The church gathers extremely large crowds of locals and visitors on August Fifteenth, which is also the Feast Day of the church.