Ffynnon Wen lies in the shadow of Gop Cairn, a massive hilltop prehistoric mound between the villages of Gwaenysgor and Trelawnyd a little to the east of Prestatyn. The mound, and the discoveries of bones from pleistocene animals including bison,reindeer, Irish elk, hyena, woolly rhinoceros and arctic lemming in nearby caves point to evidence of human occupation of the area for thousands of years, sustained possibly by the water source at Ffynnon Wen. Legends linking the location with Boudicca’s last battle against the Romans add to the mystery of the place. In keeping with its links with unwritten prehistory, there is very little recorded evidence of the uses and development of Ffynnon Wen. My only source is the 1912 record of the Royal Commission on Ancient Monuments in Wales. This speculates that Though no traditions exist respecting the cult associated with the spring, or its popularity, there can be no doubt that the name signifies the Holy Well (‘gwyn’ mutated by the feminine ‘ffynnon’ into ‘wen’=blessed) and denotes its primarily religious character. In a footnote they add that the well Ffynnon Gwaynysgor mentioned in 1698 by Edward Lhuyd is “unquestionably” Ffynnon Wen. One may speculate that, given the name is not recorded by Lhuyd, it may have been added at the time the well was being built up by the local landowner to give it some sense of spurious historical importance. Another Ffynnon Wen at nearby Henllan was given a similar treatment at a similar period. The present structure, such as it is, represents the remains of a probably eighteenth century bath house built possibly for the family of nearby Cop’rieni Hall, now Gop Farm. There was a stone enclosed and roofed well house about five feet square with steps down into the water and an adjacent dressing room. Roberts and Woodall (1902) mention a pointed stone roof.
These buildings, already ruinous when recorded in 1910, were virtually demolished soon afterwards by the tenant farmer, tired of a constant stream of visitors to the well. The square stone lined well basin remains, surrounded by stone work from the demolished buildings. The overflow from the well now creates a rectangular pool, bound by a stone and earth bank, probably a remnant of an earlier hedge or wall. 
The Clwyd Powys Archaeological Trust record for the site on the Archwilio database states that the well chamber was covered over by a late slab when seen in the 1980s. This slab is now removed, and possibly lies broken in pieces by the well. A large tree beside the well is further affecting the stonework. 
During the winter, what remains could be seen clearly, however in summer the site is hidden by nettles and brambles as Ffynnon Wen is slowly drawn back into the unrecorded prehistory of the surrounding countryside. 
Ff Wen is on private land not open to the public, although a public footpath runs close to it. All photos were taken from outside the fenced off area.
Askew Roberts and Edward Woodall (1902) A Gossiping Guide to Wales
Well Hopper 