15th Century well 'could be lost to Caernarfon bypass'
Campaigners fear a 15th Century medieval well could be lost as engineers build a £135m road nearby.
The earliest written record of Ffynnon Fair holy well, connected to Llanfair-is-gaer church near Y Felinheli in Gwynedd, dates back to 1458.
But activists are concerned work building the Caernarfon bypass on the shores of the Menai Strait could affect an "important part of our heritage".
The Welsh Government says its presence has been considered.
Work to build the Caernarfon and Bontnewydd bypass started earlier this year - almost 11 years after it was first proposed.
Construction on the new six-mile (10km) A487 relief road is expected to be completed in Spring 2021.
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But the 450-year-old landmark site is so close that the Welsh Wells Society believes the well - as it was - "was buried by stones in the last few days".
The well's origin is not certain but society secretary Howard Huws said: "It is largely an oral tradition - sometimes on maps."
He added: "In the 1970s improvements were made to Ffynnon Fair, then it is possible that the well could be diverted at that time.
"But it still started on this site until about three days ago.
"Cadw and the ancient monuments commission do not seem to be interested in this type of work so the wells are not registered and they are not protected."
The Welsh Government, which runs the Welsh historic environment service Cadw, said the well's "presence has been a consideration at every stage of the development".
"Although there are some written records which suggest that a structure stood over the well in the 1900s, no physical evidence of this have ever been identified," the statement added.
"Experts believe that the well may have been a simple spring with little or no structure but is nevertheless an important site in local history.
"Archaeological mitigation which is being undertaken during the construction of the bypass will ensure that any evidence of the well which may come to light during the works will be fully investigated and recorded."
But Mr Huws insists all wells could be affected "unless we protect these treasures."