The earliest iron implement found in Wales is a sword from Llyn Fawr which overlooks the head of the Vale of Neath, which is thought to date to about 600 BC. Hillforts continued to be built during the British Iron Age. Nearly 600 hillforts are in Wales, over 20% of those found in Britain, examples being Pen Dinas near Aberystwyth and Tre'r Ceiri on the Llŷn peninsula. A particularly significant find from this period was made in 1943 at Llyn Cerrig Bach on Anglesey, when the ground was being prepared for the construction of a Royal Air Force base. The cache included weapons, shields, chariots along with their fittings and harnesses, and slave chains and tools. Many had been deliberately broken and seem to have been votive offerings.