Stonehenge stands on Salisbury Plain in Wiltshire, a landscape of rolling chalk downland eighty miles west of London and thirty miles north of the English Channel. The monument consists of an outer ring of massive sarsen stones, each weighing up to twenty-five tonnes, brought from the Marlborough Downs twenty miles to the north. Inside this ring stand the trilithons, two upright stones topped by a horizontal lintel, forming doorways of stone that rise to nearly five metres. Scattered among these giants are the smaller bluestones, spotted dolerite and rhyolite that weigh up to four tonnes each, and which modern archaeology has traced to the Preseli Mountains in south-west Wales, a journey of over two hundred kilometres. The construction began around 3000 BCE with a circular ditch and bank, continued with the erection of the bluestones around 2900 BCE, and reached its final form with the sarsen trilithons around 2500 BCE, a period of building that spanned longer than the Roman Empire existed.

The earliest written reference to Stonehenge comes from Henry of Huntingdon around 1130, who described it in his Historia Anglorum as one of the wonders of England. But the legend that would define the monument for centuries was written by Geoffrey of Monmouth in his Historia Regum Britanniae around 1136. In Geoffrey's tale, the British king Aurelius Ambrosius, brother of Uther Pendragon and uncle of the future King Arthur, sought a fitting memorial for the four hundred and sixty British nobles who had been treacherously massacred by the Saxon leader Hengist during a truce at Amesbury. Aurelius consulted his wise men, and they advised him to seek out Merlin, the prophet of Vortigern, a man of such genius that none could match him in predicting future events or in mechanical contrivances. Merlin told the king that in Ireland, on Mount Killaraus, stood a structure called the Giant's Dance, a circle of stones of vast magnitude and wonderful quality that had been brought from Africa by giants of old. These stones possessed mystical and medicinal virtue: the giants had washed them and bathed the sick in the water, which infallibly cured them, and every stone had some healing power.

Aurelius laughed at the idea of transporting such vast stones from so distant a country, protesting that Britain was furnished with stones fit for the work. But Merlin insisted, and Uther Pendragon was sent with fifteen thousand men to fetch the Giant's Dance. They reached Mount Killaraus and found the Irish king Gillomanius defending the stones. Uther defeated the Irish in battle, and his men attempted to dismantle the circle using ladders, ropes, and every mechanical device they could devise. But the stones were too heavy, and the Irish had already proved that the monument could not be moved by ordinary means. Merlin laughed at their efforts and used his own superior knowledge to design devices that lifted the stones with ease. The stones were loaded onto ships and sailed back to Britain, where Merlin re-erected them on the plain of Ealing near Amesbury, arranging them in exactly the same pattern as they had stood in Ireland. The monument was completed, and Aurelius Ambrosius was buried within the circle, followed in time by Uther Pendragon himself. The story ends with the moral that art surpasses strength, a lesson that Geoffrey intended for his medieval audience.

Robert Wace, writing his Roman de Brut around 1155 for a Norman French audience, retold Geoffrey's tale with one crucial addition: a giant helped Merlin in the work of re-erecting the monument. A 14th-century manuscript of the Brut in the British Library shows an illustration of Merlin directing a giant in the construction, a detail that Wace invented but which became fixed in the popular imagination. The 14th-century Short Metrical Chronicle changed the patron of the work, claiming that Merlin built the Giant's Dance for King Dunvalo Molmutius rather than Aurelius, but the core legend remained the same: a wizard, a king, and stones that could not be moved by mortal hands. The name "Stonehenge" itself comes from Old English: "stan" meaning stone and "henge" meaning a hinge or a hanging place, referring to the lintels that seem to hang between the uprights like stone bridges suspended in the air. The earliest recorded form is "Stanenges" in the 12th century, and the name has always suggested something suspended, something that defies gravity and explanation.

Other legends cling to the stones like the lichen on their surfaces. The Heel Stone, a single sarsen standing outside the main circle, is said to have been thrown by the Devil at a friar who had outwitted him. The Devil, disguised as a gentleman, had tricked an old woman out of her stones by promising her as much gold as she could count while he moved them. He transported the stones to Salisbury Plain with magic and boasted that no one could tell how many there were. A local friar sidled up and said, "That is more than can be told." The Devil, enraged, threw one of the menhirs at the friar, but the stone hit the man's heel and dented, and the friar was so strong that the stone rebounded and landed upright where it stands today. Another legend says that the stones were once dancing giants who were frozen in place by a wizard's enchantment, their circle a moment of revelry turned to stone for eternity. A baker once tried to count the stones by placing a loaf on each one, but he could never get the same number twice, and the stones remain uncountable to this day. In the 21st century, archaeologists led by Mike Parker Pearson discovered that the bluestones did indeed come from Wales, specifically from the Preseli Mountains, and that the stones possess remarkable acoustic properties: when struck, they ring like bells or gongs, a phenomenon known as lithophony. The local folklore of Pembrokeshire has long held that the bluestones possess healing qualities, and the alignment of the avenue to the midsummer sunrise suggests that the monument was as much a temple of sound and light as it was a burial ground. The bodies of the dead were brought from Woodhenge and Durrington Walls, journeying down the River Avon and up the avenue to the stones, where the bluestones from the west - the direction of the ancestors - awaited them. Stonehenge is not merely a monument but a landscape of meaning, a place where the living and the dead, the mortal and the magical, the scientific and the legendary have met for five thousand years.