Stonehenge above
Photograph by Joe McNally/Sygma
At ground level, the ruins of Stonehenge appear somewhat random and chaotic, but a view from the air reveals the monument's circular order. The site started out modestly around 3100 B.C. as a wide ring of wood posts surrounded by a ditch and bank. The familiar enormous rock slabs, some brought from hundreds of miles away, were added to the interior over a period of about 1,500 years.