Hang Sơn Đoòng

The world's largest cave, Son Doong is vast enough to boast a micro-climate of its own that has spawned forests teeming with flying foxes and monkeys. This impressive cave is 5.5 miles (8.9 kilometers) long and can fit an entire city block within its cavernous embrace. The rays of light that filter through have spurred the growth of trees, while dried pools once fed by the subterranean river boast massive cave pearls. The stalagmites too are of grand proportions, measuring up to 80 meters (262.4 feet) in height. With its own jungles and rivers enclosed beneath a sky of rock, the Son Doong Cave is truly a mesmerizing destination for the adventurous at heart. The cave is notoriously difficult to reach, however, and expeditions are led by Oxalis, a local travel company that has exclusive access to the magical world of the Son Doong Cave.