Swinside stone circle, Cumbria, England. This stone circle, near Broughton-in-Furness, consists of 55 stones positioned to form a 28-metre diameter circle. The stones are porphyritic slate from the nearby hills. The circle dates from the Bronze Age, which took place in Britain from around 2100 BC to 700 BC. The precise function of the stone circles here, and elsewhere in Britain, are not clear, but it is thought they were concerned with astronomical, calendrical and religious symbolism. Most stone circle construction in Britain ceased by 1500 BC.