Son Doong  is the world's largest cave. (Photo: Oxalis)

Oxalis, the only private company licensed to explore and conduct tours of Son Doong, was allowed to reopen its services last week as Covid-19 has been brought under control in Vietnam.

Earlier, local authorities had closed all tourist destinations in the central province, dubbed ‘Kingdom of Caves’ in Vietnam.

Registration for Son Doong tours, organized between June and August this year, have to be made well in advance since stringent restrictions have been placed in order to preserve the complex’s ecosystem.

Around 240 slots are available for the rest of 2020, according to Oxalis. A four-day expedition that departs this year costs only 2,500 USD per person, down from the previous price of 3,000 USD.