Shelley's poem Ozymandias tells of the wreck of a huge rock sculpture which stands in the desert above the inscription: ''Look on my works ye mighty and despair.'' ''Nothing beside remains,'' the poet tells us. ''Boundless and bare the lone and level sands stretch far away.''
A thousand years from now, when the US empire has crumbled into dust and climate change has cleared beef cattle and farmers from the western prairie, it is possible to imagine that tourists will travel across the sand to visit the mountains of South Dakota and marvel at the massive monuments of a bygone civilisation.