South portal of former railway tunnel beneath Castle Square

The south portal of the former railway tunnel beneath Castle Square is constructed from snecked rock-faced stone and dates back to 1869. This entrance features a cast iron girder that supports jack arches within the tunnel, which is inscribed with 'de Winton & Co 1869'. Above the entrance, there is a thick roll-moulded band and modern railings positioned above the coping stones. The opening is flanked by shallow buttresses; the left-hand buttress is set back from the end, while the right-hand buttress is integrated into the revetment wall beneath Segontium Terrace. The left side wall includes four recesses with brick arches beneath a roll-moulded band that continues from the entrance elevation, topped with coping stones and railings.