This monument is located in Athens, Greece, southwest of the acropolis (37.970189, 23.732006). It was erected around 131 AD. I am not sure about the translation of the inscriptions. (They will be updated) Currently there are two interpretations regarding the inscriptions.
* They stated the seperation between two parts of the city, the older and the roman.
* They were a form of boast claiming all of the city belongs now to Hadrian
https://en.wikipedia.org/wiki/Arch_of_Hadrian_(Athens)