The ancient structure known for its massive stone blocks and alignments is Stonehenge. Located in Wiltshire, England, this prehistoric monument consists of a circle of standing stones, each around 13 feet high and weighing several tons. Historians believe it was constructed between 3000 BC and 2000 BC. Stonehenge's alignment with the solstices suggests it served astronomical purposes, possibly for rituals or ceremonies. The mystery surrounding its original function, the techniques used for transportation and assembly, and its cultural significance continue to intrigue archaeologists and visitors alike.