The Great Wall of China snakes across the mountainous North of the country for 6,400km. Photograph: Georg Gerster/Panos  Humanity's extraordinary signature on the Earth's landscape is about to be celebrated at the British Museum with more than 350 images, each capturing ways of sending the same message to future generations: "We were here." The slender scribble of the Great Wall, a citadel like a plum pudding, the tree-covered, keyhole-shaped tomb of a Japanese emperor; they make you want to reach out and touch, running your finger over the lumps and lines.  Georg Gerster, the Swiss photographer responsible for these images, couldn't do that. He started compiling his unique record of the Past from Above in 1963, clinging to helicopter struts, fighting camera wobble as light aircraft bucked and yawed, and losing valuable dawn and evening light explaining to control towers that he wasn't a spy. But he came back from more than 40 years of aerial photography with an exceptional record of monuments as their long-dead creators could only hope to see them from some celestial viewpoint in the afterlife.  Pharaoh Ramesses II, for instance, had to be content to imagine the magnificent pattern of the Ramesseum, his mortuary temple dating from the 13th-century BC, from 1,000ft up. He had only his architect's plans and the vast but partial views available from the flat desert ground surrounding it. Visitors to the museum see not only the bird's-eye view, but the striking effects of later history on the monument - and the hundreds of others alongside it in the exhibition. There is demolition, excavation, rebuilding and the gentle smothering by nature with silt, sand, trees or vines.  Gerster's epic quartering of the Earth, filming the hides of more than 100 countries, has led to fresh archaeological insights as well as these breathtaking photographs. He may not have much time for philosophy as he clings to his cameras and the aircraft, but he says: "Height provides an overview, and an overview facilitates insight, while insight generates consideration." He also adds a modest: "Perhaps."  Cosy by comparison with pictures of vistas such as the great gash in Tanzania's veldt, where humanity may have begun, Britain's landscape is also represented, with unfamiliar angles on sites such as the ruined 11th-century church in the pagan henge at Knowlton in Dorset, a village wiped out by the Black Death. But although Gerster, now 78, sheds copious new light, his panoramas have failed to trace Knowlton's church bell, stolen by the devil according to legend and buried somewhere only Satan and God could see - from on high.  · The Past From Above is at the British Museum, Great Russell Street, London WC1, 020-7323 8195, from November 16 to February 11.
A new exhibition at the British Museum shows how man has made his mark on the planet. Martin Wainwright salutes some extraordinary images.