The tour, which has beenoperated for only about a year, was ranked fifth among the 20 best toursafter receiving 24 percent of votes.
Son Doong is the onlyrepresentative of Southeast Asia and one of few Asian destinations in thelist.
The tour has beat offcompetition from several well-known places such as Arctic Bay in Greenland andSouth Everest Base Camp in Nepal.
The cave was placedbehind Mount Kilimanjaro in Tanzania, the Inca Trail leading to MachuPicchu in Peru, the Grand Canyon in the US and Thrihnukagigur Volcano inIceland.
The British TV channelsaid that due to rugged terrain, visitors were required to register for atour in advance.
Oxalis Adventure, thesole tour operator to the site, charges about 70 million VND (roughly 3,000USD) for a tour through Son Doong lasting for four days and three nights.
Since Son Doong Cavebecame an attractive tourist destination, the tours of the spectacular cave arealmost booked up until 2021.
The report said only 20tour slots remained available for 2019.
Not only in the forestand the cave, visitors can trek through 25km of mountain forest roads withuneven terrain, exploring about 9km of the cave. The tour includes the use ofvines over rocky ascents.
Although foreignvisitors make up a large number of tourists exploring the cave, the percentageof Vietnamese tourists has increased significantly, making up about aquarter in 2018.
The cave has beenrecognised as the largest in the world by three international organisationsincluding Guinness (based in the UK), the Association World Record (based inHong Kong) and World Kings (based in the US and India).
Son Doong wasdiscovered by a local in 1991 and was first explored in 2009 by a group ofBritish scientists from the British Cave Research Associationwho conducted an extensive survey. It has been open to thepublic since 2013.
The 9km-long cavesystem, which extends through a mountain, was named one of the most captivatingcaves on earth by National Geographic.
Geologists said the caveformed two to five million years ago. It contains some of the tallestknown stalagmites in the world, which are up to 70m tall and is home to both ajungle and a river, whilst it could fit a 40-storey skyscraper inside.-VNA