The early Christian buildings survived in the level below the medieval ground-level, thus a number of burial chambers have been preserved, with their decoration more or less intact. Buildings above ground did not survive, but can be reconstructed based on archaeological excavations. In preparation for an exhibition, the company SketchUcation Hungary prepared a number of 3D reconstructions.
Below you can see how a late Roman basilica was reconstructed (video showing steps of the reconstruction):
The video below presents a comparison of the reconstructed late Roman basilica of Sopiane with the similar - and still standing - structure at Trier:
The medieval buildings of Pécs - the seat of a bishopric and home of Hungary's first university - got destroyed for the most part during the Ottoman occupation, and the wars of that turbulent period. Only the cathedral is standing, but in a form much rebuilt. The following video is an attempt at restoring the 14th century topography of the town, by presenting a 3D mass-study, focusing on churches and monasteries.
Finally, this is a reconstruction of the exterior of the cathedral, as it likely appeared in the 14th century: