Stonehenge

Guardian UK: Dry spell at Stonehenge reveals secret that has eluded archaeologists - Brown patches of grass left by short hosepipe lead to 'lightbulb moment' that may confirm monument was once a perfect circle

The professionals duly took charge. Aerial photographs were hurriedly commissioned before the rain could come and remove the brown patches, and the scorch marks on the western side of the Wiltshire site were mapped, and some of the brown patches indeed tallied with where stones would have stood if the circle were complete.