The Town Gate, also called the Welsh Gate or the Lower Gate, is the most intact surviving element of Chepstow's medieval fortifications. It was built in the thirteenth century to control the main approach from the south and is unusual in that it still spans the A48 road — traffic passes through its archway daily, making it one of the few medieval town gates in Wales still functioning as a thoroughfare. The gatehouse originally had a portcullis, the slot for which remains visible in the stonework overhead.
The Port Wall extends from the castle to the southern edge of the town, enclosing what was the medieval settlement on its landward side. Most of it survives to a significant height and can be walked alongside via a footpath. The wall is built from the same pale limestone as the castle and represents a coherent scheme of town defence constructed largely in the late thirteenth century, when the town's commercial importance — it was a significant port trading across the Bristol Channel — justified the investment. Together, the gate and wall give Chepstow an unusual degree of medieval urban character that has been largely preserved by the town's failure to expand dramatically in the industrial period.