The sightseer of 4014 may have to pay a virtual visit to the Tower of London or Statue of Liberty, said a climate study Wednesday that warned of dramatic ocean encroachment on heritage sites. While modern civilisation is fascinated by the pyramids of Egypt, Rome's Colosseum and the Parthenon in Greece, much of this inheritance as well as our own cultural legacy may be lost to sea-levels rising as much as 1.8 metres (six feet) due to global warming, researchers said. Out of more than 700 listed UNESCO World Heritage sites, nearly 140 risk being flooded in 2,000 years' time, they projected in a study published in the journal Environmental Research Letters. These also include the Sydney Opera House, Venice in Italy, Japan's Hiroshima Peace Memorial and Robben Island in South Africa where Nelson Mandela was imprisoned for 18 years.