1. One of the most significant prehistoric metalwork hoards in Wales, containing cauldrons, weoponry and other metalwork from the Late Bronze and Early Iron Ages, was discovered when the lake was partly drained in 1911-1913 for the construction of a new reservoir. The long-held assumption is that this hoard was ritually deposited in a 'sacred lake'. The name of the lake, 'Fawr', meaning 'great' or big', may be significant in this context. The neighbouring Llyn Fach just to the west has never been disturbed by construction works. A nineteenth century find of an Iron Age Durotrigian coin, Mack No. 317 (silver type: GGAT01687w (archwilio.org.uk) at Llyn Fach, suggests the potential for Iron Age ritual activity at this location too.
T. Driver, RCAHMW, July 2024

2. 'Into the Iron Age across Britain, Ireland and wider continental Europe, the conspicuous deposition of metalwork became ever more associated with watery places; the bends of major rivers, natural springs, the dark waters of upland lakes and the dangerous pools of mist-shrouded bogs. Professor Barry Cunliffe writes; ‘The implication is that such locations were perceived to be the liminal spaces through which it was possible for our world to communicate with the world below.’ Springs, bogs and lakes were thought to be where waters from the underworld rose to flow into the land of the humans...

In 1909 the 12-acre Llyn Fawr lake was chosen for conversion to a reservoir due to a growing population in the Valleys. The digging out and deepening of the lake discovered twenty-one bronze and iron objects including two spectacular large cauldrons, one of which could hold 50 litres of stew – enough to feed over 100 people - a spearhead and sword, horse harness equipment and other tools. Many other artefacts were probably lost in the construction work. The Llyn Fawr finds date from the very earliest Iron Age in Britain, 800-600 BC. Llyn Fawr is a striking landscape feature to visit today. The cauldron-like setting of the lake faces out from the northernmost escarpment of the Valleys, looking north to the mountains and moors of the Brecon Beacons; it is clear the lake sat at a critical interface between territories. Rock ridges overlooking the lake may have made good vantage points for onlookers at ceremonies of deposition.' 

Extract from: Driver, T. 2023. The Hillforts of Iron Age Wales. Logaston Press. pp 104-105.

3. Link to blog by Robert Glare for the Cynon Valley Museum: https://cynonvalleymuseum.wales/2021/11/20/the-iron-age-llyn-fawr-hoard/

4. Bibliography (GGAT HER: GGAT00023m (archwilio.org.uk)

Wheeler R.E.M. , 1921 , Some problems of Prehistoric chronology , Archaeologia Cambrensis : 76 : 1-18
Wheeler R.E.M. , 1922 , Hoards of the Bronze Age from Wales , The Bulletin of the Board of Celtic Studies : I pt.II : 189-191
01/MM Record Card/OS//1955/SN 90 SW 8/;
02/PM Desc Text//Wheeler&Crawford/REM&OGS/1920-21/Arch Vol.71p133-7;
07/MM Record Card/OS//1980/SN 90 SW 8/;
05/PM Mention//Brown R.L/1979/Town Cymer Afan Hist Soc/Vol.2;
06/PM Desc Text/Antiquity/Alcock L//Vol.35 p.149-159/;
03/PM Desc Text//Fox & Hyde/Sir C & HA/1932/Arch in Eng&Wales p.138;