In County Meath, Ireland, stands one of the most mysterious ancient structures in the world - Newgrange. This massive stone tomb, built around 3200 BC, predates famous monuments like Stonehenge and the Great Pyramid . It's almost the size of a football field and contains an estimated 200,000 tons of stone. What's most intriguing about Newgrange is its unique design, including a tri-spiral symbol and a passage leading into the interior.