Where is the largest cave in the world?

Son Doong Cave in Phong Nha-Ke Bang National Park in central Vietnam is the largest known cave passage on Earth by volume. Its main chamber is over 5 kilometres long, up to 200 metres high and 150 metres wide — spacious enough to contain an entire New York City block of 40-storey skyscrapers. The cave was formed 2 to 5 million years ago by river water eroding limestone, and in places the ceiling has collapsed to form skylights called dolines, where sunlight streams in and supports its own jungle complete with trees and wildlife inside the cave. It was only fully explored in 2009 by a British caving team, though a local man had stumbled upon its entrance in 1991.