"Being200m high and 175m wide as well as 9.4km in length, this cave is estimated tofit a 40-story New York skyscraper," it said.
Son Doong,located in the Phong Nha-Ke Bang National Park, has captured internationalspotlight since it was opened to tourists in 2013.
"Itrequires two days of intense jungle trekking and river crossings to reach theentrance of Son Doong Cave," the magazine noted.
Oxalis Adventure operates the tour, with a four-day-three-nightexpedition to the cave costing 69.8 million VND (around 3,000 USD).
Only1,000 visitors are allowed to explore the cave a year for environmentalreasons, and the tour is available only between January and August.
Trekkersaccompanied by a specialist go through unique underground rainforests, kayak inrivers both above and below ground and climb a 90-meter-high wall dubbed"The Great Wall of Vietnam" with ropes and ladders.
The other caves in the list are Vatnajokull Glacier Cave ofIceland, Naica Mine Cave of Mexico, Krubera Cave of Georgia, Glowworms Cave ofNew Zealand, Batu Cave of Malaysia, Marble Caves of Chile, Tham Lod Cave ofThailand, Reed Flute Cave of China, and Škocjan Cave of Slovenia./.