The Taj Mahal will collapse within five years unless urgent action is taken to shore up its foundations, campaigners warn.
The 358-year-old marble mausoleum is India's most famous tourist attraction, bringing four million visitors a year to the northern city of Agra.
But the river crucial to its survival is being blighted by pollution, industry and deforestation.
The Taj was built on mahogany posts sunk into wells fed by the Yamuna river but its water levels are dropping by several feet a year, leaving the wood brittle and falling to bits.
Last year cracks appeared in parts of the tomb and its four 40ft (12.1m) minarets are starting to tilt.