Prior to Christianity, pagan or Celtic religions existed, and many of these were associated with water, pools, and wells. When Christianity arrived it was their practice to overwrap Christianity on top of the existing religion. So if there was a stone circle in use this would become the centre of a church, and if a well was considered sacred then this too would become the centre piece of the new church. Many early monasteries have springs, wells or pools underneath them including Strata Florida Abbey in Mid Wales.
This is said to be the location of a monk who established his small home or cell next to this well, and ministered or worshiped here. St Seiriols was a friend, and existed at the same time as St Cybi, in the 6th century, these were Celtic Christians, not connected with the church or Rome. They would have lived simply, baptised people and perhaps used herbal remedies and spells to cure some people. St Cybi was at Holyhead and also had a well and church, the later church is within the walls of the roman fort - see Caer Gybi Roman Fort.
There is an Icon, a sort of picture, that shows the Meeting of the Saints. In the icon the two saints are seen meeting at the Clorach Holy Well in the centre of Anglesey. The legend is that St Cybi was tanned facing the sun travelling East in the morning and West in the afternoon. St. Seiriol was tanned in the opposite direction his face remained pale! Hence 'Seriol Wyn a Chybi Felyn' White Seriol and Tawny Cybi!. Wikipedia also tells a version of the same story.
They are said to have met at Clorach Wells in Llandyfrydog, others say a well, or a ford that was located very near what was later to be Rhyd-y-Saint railway station SH499758.
Seiriol was said to have been the son of Owain Dunwyn of Rhos, an old kingdom and part later the kingdom of Gwynedd, North Wales near Conwy, 13 of its kings are known.
Seiriol was a younger brother of King Cynlas of Rhos and King Einion of Llŷn. His cell at Penmon is said to have been rebuilt by his brothers, as they didn't think his humble residence was good enough.
Another variation of the story says that his brothers did not feel the cell was befitting a prince and built the monastery for him.
Later he is said to have retired and moved onto Puffin Island nearby, where he eventually died and was buried. In another version of the story he moved to Puffin Island to get some piece but a number monks followed him and established another monastery there, until he sent some or all of them back. The monastic building ruins on Puffin Island are from later.
The well is a small building with most of the floor open so that you can see shallow water below, a spring feeds this with clear water from one side and it flows out under the ground so that you just see a framed area of shallow very clear water.
According to the Ordnance Survey map, the water actually originates from a spring just a little way away and then flows through the building, this does line up with the direction of flow of the water.
Within this building there are stone benches, recesses, and the door post shows where a lock bar or fixing used to hold a door shut. The walls show the remains of plaster. Outside there is a courtyard that may have been another building and next to this is the marking of where a round hut was and said to have been the site of the original cell. This building is not really ancient, and the upper structure is said to be largely made of brick and date from the 18th century while some of the lower areas are older.
This spring was a healing well and accounts into the 1800's if not later, talk of its healing properties.
The site is very quiet, and sheltered.
In more recent times I have heard that the recreated Druidic Order has classed this also as one of their holy places.
The Anglesey Coastal Path also runs past here, so its worth stopping off to take a look.
Getting there: From Beaumaris Take the B5109 to Llangoed at Tre-Castell turn right down the road to Penmon until you reach the Toll Booth park up in the car park here outside the priory.
Access: From the car park for Penmon Priory, turn left behind the wall at the end of the car park near the pay hut, past the fish pond on your right this leads to the well which is through the stone doorway into an enclosure area and the well is off to the right.