Ernest Renan makes reference to it:
"The basilica called " Ancient " or " Apostolic " in the fourth century was situated in the so-called street of Singon, near the Pantheon. But where this Pantheon was we do not know. Tradition and certain vague analogies would suggest seeking the primitive Christian quarter in the direction of the gate which still retains the name of Paul, Bab Bolos, and at the foot of the mountain called by Procopius Stavrin, which bears the south-eastern flank of the ramparts of Antioch. It was one of the parts of the town least rich in pagan monuments. The remains of ancient sanctuaries dedicated to St. Peter, St. Paul, and St. John are still to be seen here".
He draws an inference that the Singon must have been in the far north of the city, but I would doubt that the Pantheon would have been that far from the city center. He obtains this reference to the Singon from Malalas. I have seen vague mentions of this street before, one seeming to indicate that it ran parallel to the Colonnaded Street, one block distant. Whether it was on the "highside" or the "lowside" of the main street is not clear.
Edmund Thomas in his essay in the book "Pantheons" states that the only evidence for a Pantheon earlier than that of Agrippa in Rome was that in Antioch. He says that said building was rebuilt by Julius Caesar. He dates Malalas' observation (Chronicle 242, v.11) that Paul and Barnabas gave sermons on the street called Singon to events in 40 AD. He goes on to speculate that the street's name may have been Siagon (Σιαγων or "jawbone").
Jack Finegan in his Archaeology of the New Testament says that Siagon derives from the Slavonic version of Malalas and that the "jawbone" may be a reference to the street's shape. This would be the first non-straight street in ancient Antioch that we have heard of, but it could be the case on the mountain slopes where there may have been a break in the rigid Hippodamian street layout. Though anyone who has visited the ruins of Priene will know that the Greeks did not let mere topography stand in the way of a rigid application of the rule.