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The discovery of a rare and valuable wild truffle growing in a hotel's rooftop garden in Paris is a first, excited experts have said.

The find, in the roof garden of the Mercure Paris Centre Tour Eiffel hotel, near the Eiffel Tower, comes as truffle prices have doubled to more than €5,000 a kilogramme.

"The discovery of this wild truffle is a wonderful example of how roof gardens and green roofs have a huge potential for urban biodiversity," said the Museum of Natural History, which revealed the find.

The discovery suggests that the micro-climates of Paris's roof gardens might be favourable for growing truffles, the museum added. Experts from the the French Institute of Evolution and Biodiversity are now trying to work out how the truffle got on to the roof, "and whether this is a good sign of the health of the Paris ecosystem".

The winter truffle variety found in Paris is said to have a stronger, more peppery, flavour than the black Perigord truffle found in southern France, Italy, Spain and Croatia.

The capital aims to have 100 hectares of roof gardens in the next two years.