Bookings to Son Doong cave in the central province of Quang Binh are full for next year, according to Oxalis international travel company, which is permitted to pilot the adventure tour to the world biggest cave.

Four hundred tourists have booked tours to the cave next year, at least 3,000 USD each. Six hundred tourists worldwide contacted the company for the tour in 2015.

Son Doong cave was first discovered in Phong Nha-Ke Bang National Park by a local man named Ho Khanh in 1991.

The cave was then made known publicly in 2009 by a group of British scientists from BCRA, led by Howard Limbert, after their surveying trip in the park.

According to Limbert, the cave is five times larger than the nearby Phong Nha cave, previously considered to be the largest in Vietnam.

Son Doong cave is found to have a length of at least 6.5 kilometres. It is estimated to be 200 metres in width and 150 metres in height. The largest chamber of the cave is judged to be 250 metres in height.

Source: VNA