The city of Edessa has a long history as an important city.

Edessa (/ɪˈdɛsə/; Ancient Greek: Ἔδεσσα, romanized: Édessa) was an ancient city (polis) in Upper Mesopotamia, founded during the Hellenistic period by King Seleucus I Nicator (r. 305–281 BC), founder of the Seleucid Empire. It later became capital of the Kingdom of Osroene, and continued as capital of the Roman province of Osroene. In Late Antiquity, it became a prominent center of Christian learning and seat of the Catechetical School of Edessa. During the Crusades, it was the capital of the County of Edessa.

Edessa (modern Urfa), located today in south-east Turkey but once part of upper Mesopotamia on the frontier of the Syrian desert, was an important city throughout antiquity and the Middle Ages.

In the 2nd century BCE, Edessa became the capital and royal residence of Osroene, a region of the Seleucid Empire in north-west Mesopotamia which declared itself an independent kingdom (traditional date 132 BCE).

Then, after the successful campaigns of the emperor Lucius Verus (r. 161-169 CE), who sacked Edessa, the city was made into a Roman colony and, thereafter, prospered, even minting its own coinage. The city once again benefitted from its favourable position on trade routes, being on the only official route between the Roman and Parthian Empires (247 BCE – 224 CE).

In 242 CE Edessa became the capital of the Roman province of Osroene.

Edessa was attacked several times over the centuries especially by the neighbouring Sasanids, notably in 503 CE by Kavad, king of Persia (r. 488-531 CE), although his siege was not successful (the Mandylion doing its job). In the on-off wars between Persia and the Byzantine Empire (the eastern half of the Roman Empire), Edessa was once more attacked in 544 CE, this time by Chosroes I (r. 531-579 CE), but again the city stood firm. Between 638 and 641 CE, it was a different story and Edessa fell under Arab control; it would not return to Byzantine rule until the Byzantine general John Kourkouas took it back in 944 CE. The city, nevertheless, remained an important Christian centre, especially in terms of translations, manuscript production, and education. The cathedral of Edessa was described by the 10th-century CE Arab scholar al-Maqdidis as “a wonder of the world” (Bagnall, 2306).

Conquered by the Muslim Arabs c. 638 CE, it would be incorporated into the Byzantine Empire from 944 CE. Still a major Christian and cultural centre and capital of the County of Edessa, the city’s capture by the Muslim leader Zangi in 1144 CE, was the original motivation for the launch of the unsuccessful Second Crusade (1147-1149 CE) in order to reclaim it for Christendom. Following its destruction by the Muslim leader Nur ad-Din (sometimes also given as Nur al-Din) in 1146 CE, Edessa largely disappears from history, but today many fine mosaics from the city survive and attest to the wealth of some of Edessa’s citizens in Late Antiquity and the early medieval period.

It was the first state to make Christianity the official religion.

In the history of the Church, Edessa is famed for being the first state to
adopt Christianity as the official religion. … sample.pdf

It was one of the earliest centers of Eastern Christianity.

The earliest centres of Christianity in the East were: Edessa, Arbela in Parthia, and India. … in-persia/

It was a center of Christian scholarship.

At the same time that Edessa was the subject of imperial rivalries, the city still managed to become a great centre of culture and learning, especially of Christian scholarship. The city had been an early adopter of Christianity in the 2nd century CE with the first recorded church being already active in 202 CE. Edessa became the most important bishopric in Syria.

The Peshitta (Syriac translation of the Old Testament) originated in Edessa.

Thence came to us in the second century the famous Peshitta, or Syriac translation of the Old Testament; also Tatian’s Diatessaron, which was compiled about 172 and in common use until Rabbula, Bishop of Edessa (412–435), forbade its use. Among the illustrious disciples of the School of Edessa, Bardaisan (154–222), a schoolfellow of Abgar IX, deserves special mention for his role in creating Christian religious poetry, and whose teaching was continued by his son Harmonius and his disciples.

At its Christian height, there were more than 300 monasteries at Edessa.

Christianity was introduced into Edessa at an early period. In the reign of Trajan the place was made tributary to Rome, and in A.D. 216 became a Roman military colony, under the name of Colonia Marcia Edessenorum. During this period its importance in the history of the Christian Church continued to increase. More than 300 monasteries are said to have been included within its walls.

It contained many relics and was a popular pilgrim destination.

Edessa was also a popular stop for Christian pilgrims, the city boasting many holy relics such as the skeletal remains of Thomas the Apostle. Another important relic, and one considered of vital importance to the city’s well-being, was the Mandylion icon.

Today, it is a small town called Orfa.

Orfa is today the chief town of a sanjak in the vilayet of Aleppo, and has a trade in cotton stuffs, leather, and jewellery. Ruins of its walls and of an Arab castle are yet visible. One of its curiosities is the mosque of Abraham, this patriarch according to a Mussulman legend having been slain at Orfa. The population is about 55,000, of whom 15,000 are Christians (only 800 Catholics). There are 3 Catholic parishes, Syrian, Armenian, and Latin; the Latin parish is conducted by Capuchins, who have also a school. Franciscan nuns conduct a school for girls. This mission depends on the Apostolic mission of Mardin. There are also at Orfa a Jacobite and a Gregorian Armenian bishop.