The Clytha Hill series is a pleasant undulating walk of about 5 miles on 80% footpaths with 20% very small roads too. The offroad terrain is a mix of fields and tracks which can get muddy at some points so proper footwear is preferable, as is a good map to navigate around (I prefer the Ordnance Survey Eastern Beacons map 13 1:25000 which covers this area). Some of the paths can get a bit overgrown sometimes too.
Access is easy, either from Raglan to the east, or Abergavenny to the west, and there is plenty of parking at the parking waypoint below.
Clytha Castle is a folly that was built as a memorial by a gentleman named William Jones after the death of his wife in 1787. He was from a local landowner family of the Llanarth area but he moved back to the region from London and purchased Clytha Estate following the death of his wife. It was intended as a memorial of a happy marriage and a loving wife and there is a tablet at the site which states the build 'was undertaken for the purpose of relieving a mind afflicted by the loss of a most excellent wife'. But it must have been also very effective at showing off his status and wealth!
There is a reasonable amount of information regarding Clytha Castle to be found on the internet if you wish to research the site more, but at the moment it is used as an unusual holiday let.
The Cache
This cache involves finding a container and solving a simple puzzle at the given co-ordinates which will then take you to the final cache position (there is a permitted path marked with posts that go to it). Once you've found it continue on up the path to take a look at the folly.
The best place to park for this cache is at the given parking waypoint on the other side of the road where there is a proper car park (not charged).
The area is National Trust land and they gave kind permission for me to place this cache.