Take an incredible drone flight through the world's biggest cave
At a length of some 9 kilometres (5.6 miles), Hang Sơn Đoòng in Vietnam, near the Laos border, is the largest known cave in the world. Inside is a large, fast-flowing river; its own microclimate; a chamber 5 kilometres (3.1 miles) long, 200 metres (660 feet) high and 150 metres (490 feet) wide; and …
