Ffynnon Llawr Dolserau lies in moss covered woodland to the north of the A494 as it approaches Dolgellau. It is a drystone walled reservoir set into the forest floor, some 8 feet long by 6 feet wide. At its deepest point it appears to be around 6 feet deep, with a solid stone floor. Five steps lead down into the water in its south west corner. The water level can be controlled by plugging or freeing up a hole in the bottom of the well.
The well was built in this format probably at some time in the 18th century, probably as an outdoor bathing pool for a local family.
There is also evidence of an old orchard and gardens to the west of the well, suggesting it was a part of a more formal layout at one time. Llawr Dolserau was a part of the Nannau estate, the area was offered as a site for building an isolation hospital in the early twentieth century, this project did not eventually progress.
That it was used for bathing is attested by Jones (1859) who notes that the old family bathed in the pool within living memory.
There is however, a suspicion that the pool may have had other uses. Jones records that by 1859 the pool had been filled in with stones in order to stop people coming to the well to work magical charms. This may suggest that there was a memory of healing properties surrounding the well or that it had become a location for cursing. There is no other evidence to support either, but clearly a local need was seen to have the well closed.
The well has been reopened and cleared twice since then, initially at the start of the 20th century, and later in 1985 a local historian took on the well and cleaned it out and sections that had collapsed were rebuilt. At present it does appear that the well is maintained to some degree, it was clear of debris at the time of my visit.
Cofiadur (Owen Wyn Jones?) (1859) Chwedlau a Thraddodiadau Plwyf Llanfacraith. Taliesin. Vol 1 Part 2, August 1859.
Gryffudd, Eirlys (2005) Ffynhonnau Ardal Dolgellau. Llygad y Ffynnon, 19.
Ffynnon Llawr Dolserau SH 7595 1994
Well Hopper 
It looks a very well made and substantial well and interesting that it had domestic and charm associations.
It is fairly common – in the UK holy wells were generally suppressed after the reformation and although sometimes customs continued, often they fell into some level of disuse or reduced use. in the C18 outdoor bathing became popular and springs were converted into plunge pools for the local gentry. This seems to be the case. So it’s not really clear whether traditions or memories of traditions continued in parallel to the domestic uses, i suspect we’ll never know. But as it stands it is a well preserved and substantial well.