Sơn Đoòng Cave, the world’s largest cave in Quảng Bình Province, has been listed among “20 record-breaking natural wonders” by the US news site Insider. — VNA/VNS Photo

HCM CITY — Sơn Đoòng Cave, the world’s largest cave in Quảng Bình Province, has been listed among “20 record-breaking natural wonders” by the US news site Insider.

Sơn Đoòng Cave is part of the Phong Nha-Kẻ Bàng National Park, which is estimated to be between 400 million and 450 million years old.

The nine-kilometre-long cave was declared the world’s largest and opened to tourists in 2013, four years after members of the British Cave Research Association finished their exploration.

Registration for Sơn Đoòng tours is organised between June and August this year by Oxalis, the only private company licensed to explore and conduct tours of Sơn Đoòng.

There are only about 240 slots for the tour this year. The number of visitors are limited because of restrictions to preserve the complex’s ecosystem.

A four-day expedition this year costs US$2,500 per person, down 16.6 per cent from the previous price of $3,000.

Sơn Đoòng is the only Southeast Asian representative in the list of record-breaking nature wonders, which also includes the Angel Falls in Venezuela, the world’s tallest waterfall; the world’s longest Nile River in Africa; Mount Kilauea, the world's most active volcanic mass in the US, and Mount Everest, the world’s highest mountain. — VNS