You can tell a cave is pretty spacious when it accommodates a jungle and a river within its walls — as is the case for Vietnam’s Son Doong. However, despite its jaw-dropping proportions, the world’s largest cave has seen fewer visitors than the summit of Mount Everest. Just 640 people are permitted to visit Son Doong in 2017 and, understandably, these limited spaces are highly sought after — 300 spots were snapped up within 20 hours during the first round of sales in August.
The second lot of tickets will be available for purchase on 15 November, each costing a hefty 67,500,000VND (£2,330). Oxalis Adventure Tours is the only operator permitted to run tours to the cave. Each five-day tour requires more than 25 porters and cooks, a tour guide, two cave experts and two park rangers. The expedition includes camping, caving, knee-deep river crossings and 31 miles of trekking.