Take the road north off the A48 which runs through Parc-Seymour. (A bit further down the A48 is Penhow Castle which is now closed to the public but can be seen from the main road). Take the lane north out of the village and park in the small layby next to a new wooden gate leading to the public footpath (signposted Arcade Road). Follow the footpath up the hill for a few minutes and then try to make your own way to the top through the bushes on your left (the footpath runs around the base of the Hillfort. I only got so far up as I was carrying Dafydd and the bushes / brambles / ferns were waist high. However, I did make our what appeared to be ramparts through the undergrowth. Probably one of those sites best visited in the Spring / Autumn?
Castell Prin lurks on the steep rocky hillside inside its wood. The Coflein record describes it as defended enclosure with a bank and ditches, probably from the Iron Age. I think the name means means something along the lines of 'empty/deserted fort'. There is the stone base of a structure 4x3m: perhaps the site was reused over time. A footpath does run to the south of the fort, from one side of the hill to the other.