Instead of a path or stream, could it be a sliver of smoke from a sacrificial altar or other burning at or near the entrance at the front? And thereby preserving the perspective that this is a 45 degree top-view of a courtyard-esque thing?
I am pretty sure it is a path because around the same time Pius and other Emperors had coins minted at Samaria showing a path leading to an alter on the Mount Gerizim coinage, like below. Judaea, Neapolis. Elagabalus, AD 218-222. Ae 21.5mm, 10.3gm. Mount Gerizim surmounted by temple and altar, stairway to temple and colonnade below mountain.
Honestly I think there are two different things being depicted on these coins. On the surface it appears that there is a 'courtyard' and a 'mountain' type. Its possible over time the lines became blurred, but one would have to do an actual study of the coinage to determine this rather than just our simple speculation. It's possible that archaeological surveys might add some light to this, but as Zeugma is now under a lake it might be difficult. I dont have Butcher. What does he have to say about this note? Why Antioch when the legend clearly states 'Zeugma'?
It appears to be because of shared obverse dies... Here's what Butcher says about it in the section on Philip's AE Antioch coinage: And Philip's AE Zeugma coinage: And along the conversation of grove of trees vs hill, this is what Butcher says on the subject:
Also posted a coin yesterday from Cyrrhus that butcher believes was minted at Antioch see description below pic. SYRIA, Cyrrhestica. Cyrrhus. Philip II. AD 247-249. Æ 29mm (15.88g, 6h). Laureate, draped, and cuirassed bust right / Zeus Kataibates seated facing below garlands, holding thunderbolt and scepter, eagle at his feet to left, within hexastyle temple with arched pediment; above, bull (Taurus) leaping right. Butcher 21 var. (bull leaping left); SNG Copenhagen 49 corr. (under Philip I, bull not described); BMC 34 corr. (bull described as ram; same rev. die [obv. not illustrated]). VF, brown patina. Butcher notes that obverse dies of Philip for Cyrrhus are shared with Hierapolis, Zeugma, and Samosata and suggests that the coinage under his reign was struck at Antioch.