There’s not much to modern Trabzon, a small, dusty port city on Turkey’s Black Sea coast best known for hamsi, the humble anchovy. But it was here, in 1461, that the final vestiges of the Roman imperial tradition, inaugurated by Augustus nearly 1,500 years earlier, came to an end, swept aside by the growing might of the Ottoman empire.

This coda to antiquity starts in 1204. While Enrico Dandolo’s Venetian-led Crusader army was in the process of sacking Constantinople and deposing the Byzantine emperors, a thousand kilometres down the coast a new state laying claim to the Eastern Roman empire was taking its first steps under the Comnenos family, one of Constantinople’s foremost dynasties. This Empire of Trebizond, as Trabzon itself was known, would last for 250 years, under the longest uninterrupted dynastic reign of any Byzantine family.

The origins of the Comneni’s reign in the east are murky, but the general account runs as follows. When Andronikos I Comnenos, reportedly known as ‘misophaes’ (hater of sunlight) due to the number of people he blinded, was deposed from the Byzantine imperial throne in 1185, his grandsons Alexios and David were somehow spirited out of Constantinople to Georgia and the court of Queen Tamar. This was the height of the so-called Georgian ‘golden age,’ which featured a flowering of power and culture in the Causcasian kingdom.

As to why Tamar accepted the fugitives is contested, with some chroniclers suggesting some form of blood relation between the Georgian royal family and the Comneni, and others a dispute with the new imperial family back in Constantinople. Whatever the connection, it was enough in 1204, just a few weeks before the Crusaders took Constantinople, to furnish the brothers with the military means to seize Trebizond, with Alexios the first ruler of the new empire.

Trebizond itself was well-known in antiquity, having been founded first half of the eighth century B.C by Greek settlers. The combination of its naturally defensive topography and the riches from its silver and gold mines made Trapezus (as it was then known) one of the wealthiest of the many settlements that ringed the Black Sea, and it was on this foundation that the ‘Megas Comneni’ build their power. At its height, the empire stretched west to Sinope, another former key trade entrepot midway between Trebizond and Constantinople, and east to the borders of Georgia.

Although mainly concentrated around the coast, it also penetrated inland, although the natural barrier of the Pontic Alps proved a physical border for the kingdom. This inland region, known as the Matzouka, was made up of a series of mountainous valleys guarding the approach to the imperial seat. The Orthodox culture of the new empire fell on fertile ground, and has been preserved by sites such as the monastery complex at Soumela, carved high into the mountainside. This was a Greek-speaking, Christian kingdom, and indeed until the twentieth century remained that way: in 1920, it was estimated that three-quarters of the population of the region retained that legacy.

Trebizond thrived through accidents of terrain. Its position in the south-east corner of the Black Sea made it a key node on both the Transcaucasian Silk Road and the overland trade route to Persia to the south, and by the mid-thirteenth century it was established both in the wider, global imagination and in the power networks of the era. It is known that the Trapezuntine court received an embassy from Edward I of England in that century; later, Cervantes’ Don Quixote would dream himself the emperor of Trebizond. In its day, as historian Charles King puts it, the empire was ‘an intriguing and almost mythical mixture of the decadence and splendour of the Orient with the otherworldly piety of the Christian churches of the east.’

Above all else, the Comneni had a secret weapon that enabled them to retain their power in the region for as long as they did: their daughters, known at the time for their legendary beauty. These the emperors married with abandon to a whole host of neighbouring rulers and strongmen, a strategy tying the Comnenus bloodline to a host of dynasties, including that of the Safavids in Iran. Such a policy reached its zenith under Alexios III in the fourteenth century, who married off four of his five daughters to figures such as Bagrat IV, king of Georgia, and the Muslim emir of Sinop, Tadjaddin Pasha.

Even with this strategy in hand, the empire was not to last. The rise of the Ottomans spelled the beginning of the end for the dynasty, and after Constantinople fell in 1453 it was only a matter of time before it would be the turn of the Comneni. There were dreams across Christendom of a Byzantine restoration led by the Trebizond royal family, but even as embassies were ranging across Europe in support of such a mission, Mehmet II swept down from the hills and put Trebizond to siege. A month later, the city was taken, and with it the last embers of the Augustan project were snuffed out for good.

Although it never played so great a role again, Trebizond was not destined for anonymity, with its strategic position for transcontinental trade ensuring its afterlife. Indeed, in the 1800s, increasing competition among the Great Powers for control of trade routes to Persia saw a brief second flowering of the city: at one point, Britain’s nineteenth-century P&O shipping company even ran a direct line from Southampton to Trabzon. All the while, the region retained its distinctly Greek flavour – but this too was destined to end with the Greek-Turkish population swap of 1923. Only up in the monasteries of the Matzouka does the dream of Byzantium remain.