The site of Pistyll Dewi is depicted on first edition Ordnance Survey mapping, with the site of St Mary's Well (NPRN 423502), outside the external wall of Cathedral Close at St Davids Cathedral (NPRN 306). Another source, however, records it as being within the churchyard. The well is traditionally assigned to St David, who prayed to God for a new well during a drought. No trace of the well was visible in 1966.

Sources include:
Dyfed Archaeological Trust, Historic Environment Record

N Vousden, 26 October 2018