At Gawri in the Zagros Mountains, on the western frontier; possibly Partho-Sasanian but the date is currently very uncertain:
https://www.cambridge.org/core/journals/antiquity/article/gawri-wall-a-possible-parthosasanian-structure-in-the-western-foothills-of-the-zagros-mountains/C0BAF0AB27D9349C3DAD4D9F33F5324C
QuoteThe wall runs from north to south over the western mountains of Sar Pol-e Zahab, extending almost 115km ... The poor preservation of the wall precluded exact measurement of its width and height, but we estimate it to have been four metres wide and approximately three metres high. Remnants of structures, now destroyed, are visible in places along the wall. These may have been associated turrets or buildings.