In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Pentrefoelas like this:
PENTREVOELAS, or Capel-Voelas, a village and a parish in Llanrwst district, Denbigh. The village stands on an affluent of the river Conway, near the boundary with Carnarvon, 8½ miles S S E of Lanrwst r. station; is a resort of anglers; and has a post-office under Llanrwst, Denbighshire. ...
The parish comprises 8, 144 acres. Rated property, £2, 200. Pop., 534. Houses, 95. The property is divided among three. Voelas Hall is the seat ofW. G. Wynn, Esq. Castell-Coch, near V. Hall, was an ancient fortalice, reduced by Llewelyn; and is now represented by an earthwork. An inscribed standing-stone also is there; and is supposed to mark the grave of Llewelyn-ap-Sitsylt, slain there in 1021. The living is a p. curacy in the diocese of St. Asaph. Value, £242.* Patron, W. G. Wynn, Esq. The church was rebuilt in 1859.
GB Historical GIS / University of Portsmouth, History of Pentrefoelas, in Conwy and Denbighshire | Map and description, A Vision of Britain through Time.
Date accessed: 30th April 2017
Click here for more detailed advice on finding places within A Vision of Britain through Time , and maybe some references to other places called " Pentrefoelas ".