Built to mark the Golden Jubillee of George III in 1810 by Thomas Johnes, owner of the nearby Hafod Estate, the Arch (which is about one and a half miles from Devil's Bridge on the A4574) marks the point where the road across the Cambrians to Rhayader becomes the 'mountain road'. Until only a couple of years ago the road ran through the arch. Now bypassed, it's safe from the ravages of traffic. There's a picnic area with parking and loos by the arch, and three waymarked trails through wild upland countryside start from here.