We compare Uggeri to Wilber in another commentary. As we noted there Uggeri has the former branch of the Orontes, that created the Island as a separate quarter, running along the Theodosian Wall. It had never seemed clear to us why Wilber's map had the Theodosian Wall cutting the old Seleucid city in half and leaving the Regia and Agora seemingly outside the reduced city. However, if we take it that the new wall was built along the watercourse, as would seem natural, then there is a rationale for the Uggeri version.
While Uggeri does not show the Regia on his map he does speculate in the text that the so-called Byzantine stadium that was uncovered in the 1930s on the Island was connected in some way to the Regia. While this clashes with our previously stated suspicion that the Regia was in the Seleucid city (correspondeing with the Casianus Church and the legal complex). Maybe, as we speculated before, the palace of justice was somehow distinct from the Royal Palace (Regia). This would allow the possibility that the Regia was built on the Island and yet in relative proximity to the "old" city due to the Island being elongated, as per Uggeri, rather than roundish in shape as Wilber drew. We suspect the latter was due to Libanius' suggestion of the Island being round in shape with its wall surrounding it like a crown. This may have just been artistic license.
The Hungarian map (for which we still do not have a source beyond the Hungarian posting on Antioch in Wikipedia) shows a Regi Templom in the same general area as Uggeri speaks of the Regia being. However, the rationale behind this remains unknown.