Tourists are flocking to the Black Diamond cave in southeast Iceland.
According to local guide Reynir Arnarson there can be as many as "300, 350, 400 people at once [in the cave] if all trips are full".
While the caves are a top-rated tourist attraction in Iceland, melting glaciers pose a threat to visitors.
There is an incentive to find new caves every year to ensure tourists' safety however the ice caves can only be visited on a guided tour.
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