Dr Jonathan Foyle, chief executive of the World Monuments Fund Britain, which is handling the work, said it was like finding a "subterranean wonderland".

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For example, he said the World Monuments Fund has placed a local 400-year-old church on its watch list because of the application sent by the resort.

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In October 2011, the ruins were placed on the World Monuments Fund's Watch List, a catalogue of cultural heritage sites around the globe which are in danger.

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Erica Avrami, research and education director at the World Monuments Fund (WMF) agreed that countries need to be properly equipped so the influx of travellers does not overwhelm local communities or heritage sites.

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But a tourism plan developed by the World Monuments Fund with local authorities in 2011 limited the number of tourists who can visit Phnom Bakheng at sunset to 300 per day and promoted visiting at other times of the day to alleviate the rush.

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