It has been growing for millions of years.
Son Doong cave, the largest in the world, rises in places to 200 meters high, the equivalent of forty-story skyscrapers.
For eight years, it has been open to the public.
To preserve it, only a travel agency, Oxalis, is authorized to show it around, a good way to limit the number of tourists.
They are only a few hundred to be able to enter each year, for a price ranging from 50 euros the visit, to 2,500 euros the four days of exploration.
But this unique ecosystem is threatened today.
A cable car project to Son Doong has been abandoned, but another to get to a cave 3.5 kilometers away is still under consideration.
This will cause “a radical change in the nature of the tourist offers proposed (...) and will certainly have irreversible impacts on the largely virgin environment” of the site, warned UNESCO.
In addition, due to the Covid-19 pandemic, foreign tourists have deserted Vietnam.
Their number fell by nearly 80% in 2020 compared to 2019, when they were 18 million, a record.
To bring them back, the country could develop infrastructure there, experts worry.
The authorities have put in place "very good protection policies, but often they ignore them" and do not take them into account in reality, notes Peter Burns, a consultant who worked on a sustainable tourism project in Vietnam.
Tourism projects that would also harm the 500 locals - guides, porters, owners of small accommodation - who live thanks to Son Doong.
