Mynydd Rhiw is an upland area, its highest point 304m above sea level, dominating the south-western tip of the Llyn peninsula. The geology of the mountain comprises ridges of hard volcanic rock, interspersed with a finer-grained shaley rock

A number of archaeological features survive on the mountain. Survey and excavation across the northern extent of the mountain (centred SH 234 298) has revealed the extensive remains of a Neolithic stone axe factory (NPRN 302263) for which radiocarbon-dating suggests that the hill was visited for this purpose from 3,650 BC until about 3,050 BC. Evidence of Bronze Age activity relate to a group of 6 Bronze Age cairns (NPRNs 308048, 308047, 302261, 302262, 302257, 421096) all in varying states of preservation, some having been robbed during the creation of the surrounding enclosure wall and others having structures/shelters constructed in them. Two linear banks also cross the summit of the mountain, one is a parish boundary (NPRN 421094) which is thought to have earlier antecedents and association with an `early? looking bank (NPRN 421095) aligned to it.

Louise Barker, RCAHMW, July 2015

Sources
Barker L. and Burrow S. 2008 Neolithic Manufacture: The Mynydd Rhiw Axe Factory. In Wakelin P. and Griffiths, R. (ed) Hidden Histories. Discovering the Heritage of Wales. RCAHMW
Burrow, S. 2011 The Mynydd Rhiw quarry site: Recent work and its implications. In Davis, V. and Edmonds M. (ed) Stone Axe Studies III. Oxbow
Houlder, C.H. 1961 The excavation of a Neolithic stone implement factory on Mynydd Rhiw in Caernarvonshire. Proceedings of the Prehistoric Society vol. 27, 108-143.