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):
