"In May 1937, as a result of some work undertaken by the municipality in connection with the streets, a drain, paved with large basalt blocks, was discovered in the immediate neighbourhood of the bridge. Permission was obtained to make a trial excavation and street pavement of the period of Justinian, covered by a medieval road, was found only a few feet below the modern level. This pavement was bounded by a heavy wall, 2.10 m. thick, composed of very large blocks, It was exactly parallel to the axis of the present bridge and if extended, would have covered the sidewalk on the left (south) side of the bridge. A still heavier wall, 2.35m. thick and coming from the east, formed an obtuse angle with the first wall and is, in all probability, the fortification wall of the city of that period. It was not possible to establish the presence of a gate in the area uncovered by the trench, but it is almost certain that there must have been one at or near the bridge, which is modern in its upper part, but ancient below, is at least as old as the sixth century and in all probability very much older."
Alas the bridge referred to (pictured above in 1872) fell victim to "urban improvement" in the 1960s. So a structure that had withstood maybe 2000 years of earthquakes and wars was replaced by a jerrybuilt structure that will probably succumb to the next "Big One" when it hits Antakya. Below is a map (Weulersse's from the 1930s) of the site of the Bridge Dig.
I already had divined that there had been a brief bridge excavation, from the Princeton photo archive where the still unpublished photos of this minor dig are listed. While small-scale, it fascinates me because it may be the first clue on the scale of the Seleucid Wall, for which no other parts have been uncovered. It also is intriguing because the find (at the river bank) was "several feet" below the modern surface while a mere couple of hundred metres away the dig at the Nejjar mosque had 11 metres of overburden.
This reinforces my suspicion that the Greek city was originally much flatter than the current town and that descending material from the mountain and the accumulation of debris from 2000 years of occupation has created a sloping urban landscape. If the street level at the riverside is pretty much around where it has always been then that implies also that the ruins of the Greek city around this area should be quite near the surface. Amongst these ruins would be the Seleucid agora, which we have seen mentioned as being near the river, and the Shrine of Tyche which was apparently also near the riverbank.
The photo above shows a view from the west side of the river towards the old town in the 1930s. The dig was at the far end of the bridge. The site of the 1937 finds now lies under what is probably the busiest intersection in the city where all the traffic flows from the old town to the new town across the river, with the implication that it would be unlikely that any extensive excavations are likely in the short-term without major disruption, despite the ruins being so close to the surface.
It would be fascinating to get an actual plan of the dig and eventually see the photos thereof.