The cathedral and pilgrimage church of Agia Sophia (The Wisdom of God) is at the historical center of Thessaloniki, at the square with the same name, at the intersection Agia Sophia and Ermou streets. Dedicated to Wisdom and the Word of God is, together with the churches of Agios Dimitrios and Acheiropoietos, among the most important Early Christian monuments of Greece and of the Orthodox world in general.

Architecturally, the church belongs to the type of transitional cross-in-square church and is a development of a basilica with a dome.

There are remarkable mosaics surviving at the monuments, in the area of the altar and the dome, which date from there different periods and are excellent examples of Byzantine art:

The abstract decoration of the semi-cylindrical apse of the altar area (cross in glory, fire and geometrical shapes) belong in the first years of Iconoclasm (726-787), as testified by the inscriptions that mention the names of empress Irine of Athens and her son Constantine VI, who ruled jointly in the years 780-788. Here, we can discern the name of bishop Theophilos. The inscriptions are related to the visit of the emperors in Thessaloniki, just before the 7th Ecumenical Council in Nicaea in 787, which decided the end of Iconoclasm.

The majestic representation of the Ascension of Christ at the dome belongs to the second stage and more specifically in the end of the 9th century. It depicts Christ in the centre of a glory, supported by angels, while lower stand the figures of the apostles. Among them Virgin Mary, surrounded by two archangels pointing to the Divine Presence at the celestial dome.

The mosaic of the enthroned Virgin Mary holding baby Christ, at the conch of the apse, which replaced a cross, belongs to the third stage, and more specifically in the 11th-12th century.

At the narthex windows, there are parts of wall paintings of monk saints of the 11th century, among then Agia Theodora in Thessaloniki.

Evliya Celebi wrote about Agia Sophia in 1667: “It was imperative for Thessaloniki, an important administrative, economic and ecclesiastic centre of Byzantium, to have its own Agia Sophia (Holy Wisdom) equal to the church of Agia Sophia in Constantinople. The surviving church was built in the mid 7th century on the site of an Early Christian basilica, and it served as the city Cathedral.

The length of Thessaloniki’s Agia Sophia is one hundred and seventy-five paces. Its width, another hundred and twenty-five. The building is unique of its kind. On the left as you enter is there is a superb green pulpit – a rare work of art – is known to all travelers by land and sea as one of the most admirable monuments in the world”.