Terrace arch and associated garden walls at Gwydir Castle

The terrace arch and associated garden walls at Gwydir Castle are constructed of slate rubble, which was originally rendered, with traces of pink and buff sandstone dressings and large dressed slate-stone coping slabs. The arch is approximately 1 meter thick and 4 meters high. It features a fine sandstone inner arch that is slightly recessed within a round-arched opening, with simple bases and imposts, and slightly sunk-panelled sides.

On the Dutch Garden side, the voussoirs have plain projecting roundels, while those on the terrace side are carved. The initials "I.W." flank a carved eagle at the top, all contained within shields, with fleurs-de-lis and lion rampant heraldic badges on the sides, completing the components of the Wynn arms. Above the arch is a shallow pediment with rounded and stepped edging to the capping stones. Sandstone obelisks, which have been reduced in height, flank the pediment on plain bases, with an additional obelisk at the apex of the pediment.

The ground level is lower on the Dutch Garden side, accessed by a stepped descent of 6 slate steps, with low moulded sandstone strings featuring simple projecting arched ends. The wall steps down on either side of the arch; to the left, it runs for approximately 5 meters before returning at a 90-degree angle to join the corner of the castle's north wing, with coping as previously described. To the right, the wall continues for about 7 meters before stepping down. This section is the highest at 3 meters on the Dutch Garden side, with a neatly finished end coping stone. The stepped-down section is half the height and has plain capping, although the center is partially collapsed. The wall continues for another 7 meters before ending in a large square pier with plain capping.