Mysterious circles of megaliths (large monumental stones) have intrigued us for millennia. These enigmatic and often elaborate stoneworks are scattered around the British Isles, parts of Europe, Africa and the Middle East. Some were built for ceremonial reasons, others as ancient markers or astronomical instruments, and some for burials or social gatherings. As a new discovery is unearthed concerning Stonehenge in the UK, we take a look at the mysteries behind these stone structures.