The subject of this study is the ruined church uncovered in the year 2011 in the south-western corner of the Alba Iulia medieval fortress, in front of the St. Michael Roman-Catholic Cathedral. The following text briefly relates the circumstances of its discovery, its archaeological context, its place in the history of architecture and the historical connotations. The ruins of the church were unexpectedly uncovered during the structural works, in the spring of 2011. The ensuing four months long archaeological investigation uncovered a church with a ground plan in the shape of a Greek cross, consisting of a semi-circular apse and a rectangular nave with a central square demarcated with four pillars. The foundations were built mostly of river stone mixed with occasional fragments of limestone blocks and bricks salvaged from the nearby Roman ruins, all of them held together with clay or/and with mortar. A thick layer of crumbly white mortar, consisting mainly of quicklime granules, formed the basis for an elevation made of coarsely carved limestone blocks, probably mixed with bricks. The ruins have a complex stratigraphic context, consequence of the high-constant use of the area during the last two thousand years, its usage reaching the highpoint at the beginning of the second millennium. Prehistoric, Roman, postRoman, Gepidic, and 8th-10th centuries’ habitation evidence was found beneath the church, which was in use for about a hundred years, until it was in turn pulled down during the second half of the 11th century, when the first RomanCatholic Cathedral was being built. Subsequently, the ruins were disturbed and partly destroyed by the 11th-13th centuries’ medieval graveyard and later still by numerous medieval and modern intrusions. A brief examination of the Byzantine architecture of the age points out that the church belongs to a planimetric design which emerged in Constantinople at the end of the 9th century and spread afterward on a large area, both within the Empire and beyond its borders. The church stands out by its particularly large apse, with pillars placed according with its axis, and so we may consider it fits in a new variety of the cross-shaped plan. This is hardly surprising since in the specified timeframe, alongside the established models, reiterated throughout the whole Byzantine world, we often find anomalies. The historical context of this discovery is a complex one, since the structure dates from a time when a vague Bulgarian presence was being replaced by an effective, stable Hungarian presence on the Mureș Valley. Historical, architectural and archaeological data imply that the church has been built in the context of the diminishing Bulgarian authority and increasing Byzantine influence in the Danube region, towards the middle of the 10th century. A stonework church with a ground plan following Byzantine patterns, of an impressing size for the age in which it was built, reflects the great importance attributed by the Empire to this region of Southern Transylvania, probably seen as a promising vanguard for the missionary work of Christianising the Hungarians. The ruins of a religious building cannot be compared with a hoard or with an isolated earring: it was the upmost manifestation of the cultural and spiritual Byzantine penetration in those border regions which were still drawing the Empire’s attention. At the same time, this discovery confirms the importance of Alba Iulia as the core of a local political entity, significant not only for its autochthonous population but also for the great powers interested at the time to consolidate their influence in the region: the Bulgarian Empire (9th-10th centuries settlement with burial grounds), the Byzantine Empire (missionary work, aid in organising the church and in erecting the cult edifice) and the Hungarian Crown of King István (conquest of the city, subsequent transferral to Alba Iulia of the seat of the Roman rite Transylvanian Diocese). The political, military and religious control of the city must have implied authority over a significant territory on the Mureș Valley. The church uncovered in the year 2011 in Alba Iulia is the oldest Byzantine style church of which we know of north of the Lower Danube: from the 6th century until the 12th century we know of no other Christian religious buildings in the area. Taking into account even the actual Byzantine lands, it is one of the very few churches that can be dated in 10th century. For this reason it may be an important factor not only when studying the history of Transylvania and Hungary, but also when studying the evolution of the Byzantine architecture.

Keywords: Byzantine church, 9th-11th centuries, Alba Iulia, Transylvania, First Bulgarian Empire, Christianisation of the Hungarians, Hierotheos