Remarkable new scientific research at Stonehenge has revealed an extraordinary new mystery. Mineralogical tests on the massive six-tonne stone at the heart of the monument show that this central rock, known as the altar stone, was brought to Stonehenge from the far north of Scotland. The altar stone is arguably the most ritually important stone in Stonehenge, because it is the rock that marks the intersection of the prehistoric temple’s two most important celestial alignments – the winter solstice sunrise to summer solstice sunset alignment, and the summer solstice sunrise to winter solstice sunset alignment.