It comprises the hamlet also called Llanddeiniolen, and the villages of Deiniolen, Bethel, Dinorwig, Rhiwlas, Brynrefail and Penisarwaun.

[1] Also in the community is the dispersed settlement of Fachwen, located on the north shore of Llyn Padarn.

[2] Castell Llanddeiniolen, some 900m west of Rhiwlas, is a hill of glacial drift whose sides have been dug away to give a steeper slope.

[4] It is thought that it was part of the territory of the Ordovices tribe, and the element -orwig, -orweg has been derived from the tribal name Ordovices;[5] although this idea was rejected by the linguist Melville Richards for lack of a sufficiently early record of a form *Orddwig..[6] In 77 CE, at some unknown location in the territory of the Ordovices, the Roman governor Agricola led his troops up a hill to a decisive victory.

He collected a force of veterans and a small body of auxiliaries; then as the Ordovices would not venture to descend into the plain, he put himself in front of the ranks to inspire all with the same courage against a common danger, and led his troops up a hill.