The Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW; Welsh: Comisiwn Brenhinol Henebion Cymru) is a Welsh Government sponsored body concerned with the archaeological, architectural and historic environment of Wales, based in Aberystwyth. It was established in August 1908, shortly after the equivalent Royal Commission on the Ancient and Historical Monuments of Scotland (February 1908), and before that for England (October 1908).
More information on the Wikipedia page [1].
The website is [2].