St. Noe's Well (the small pool on the map) is ~29ft (8m) in diameter*, which seems about right, but has three features that argue against it as a contender: it's just on the wrong side of the Wye; it has a stream issuing from it; and it has the name of a celtic saint, which seems therefore likely to have been extant when the Historia was compiled. Similar contenders include: Finnoun Arthur Guinna/Guinva(/Villa in 1309?) which was 1.5 miles East of Llanfihangel-yng-Ngwynfa. This has now been filled, but was over 12ft (3.3m) wide and 4ft (~1m) deep, and was surrounded by stone walls(*p.202); Trinity Pool (Ffynnon y Drindod) Llandow, South of Newport, which is 10m by 4m (36ft by 14ft) and 1m (3.6ft) deep. This is embanked, but is the start of the river Alun(*p.213); and, on the basis of location, Newcastle Well (location left by pub, 1st gate on left) the hollow for which is now filled with rubbish(*p.164). There is no other information on this well save its "use goes way back into pagan times". The name presumably only goes back to the construction of the Norman castle. Undoubtably, there are many other such ponds that have gone unrecorded in modern lists, or have filled.