Foel Fenlli is situated in Denbighshire, North Wales. The summit is at an elevation of 1,676 ft (511 metres), and is marked by a large cairn. Foel Fenlli is the second highest peak of the Clwydian Range.
A path leads South to the summit from the car park at Bwlch Penbarras, which is also a popular starting point for ascending Moel Famau to the north. The Offa's Dyke Path runs around the western slopes.
The remains of a hill fort about ten hectares in area are found on the peak; the site is believed to date back to the Iron Age but was later reoccupied during the Dark Ages. The "iniquitous and tyrannical" king Benlli (after whom the mountain was named) probably lived there c. 450. He was admonished for opposing Saint Germanus, and he and his castle were "consumed by fire from heaven", so the legend goes.
There are the remains of strong ramparts on all sides, with an entrance at the west end. In the south-west quarter of the fort enclosure are about two dozen hut platforms; there is a spring close to the centre.
This cache and other similar caches were originally placed by CharlieG0PZO for Radio Amateurs,who are taking part in the "Summits on the Air" programme. As they are hidden on mountain tops they will be of interest to geocachers who are fell walkers.