 In 1912 a hoard of 24 late Bronze Age weapons and tools was discovered during construction work at the Llyn Fawr reservoir , at the source of the Rhondda Fawr . The items did not originate from the Rhondda and are thought to have been left at the site as a votive offering . Of particular interest were fragments of an iron sword which is the earliest iron object to be found in Wales and the only ' C @-@ type ' Hallstatt sword recorded in Britain . 
