Designated a Unesco World Heritage Site in 2003, the remarkable Phong Nha-Ke Bang National Park contains the oldest karst mountains in Asia, formed approximately 400 million years ago. Riddled with hundreds of cave systems – many of extraordinary scale and length – and spectacular underground rivers, Phong Nha is a speleologists’ heaven on earth, and a real treat for anyone who appreciates the sight of nature at its most raw.

　　The caves are the region's absolute highlights, but the above-ground attractions of forest trekking, the area's war history, and rural mountain biking means the park has enough going on to warrant stays of up to three days.

　　Documented exploration of the caves parks only began in the 1990s, led by the British Cave Research Association and Hanoi University. Cavers first penetrated deep into Phong Nha Cave, one of the world’s longest systems. In 2005 Paradise Cave was discovered, and in 2009 a team found what is considered the world’s largest cave – Son Doong. In 2015 public access to two more cave systems was approved.

　　Above the ground, most of the mountainous 885 sq km of Phong Nha-Ke Bang National Park is near-pristine tropical evergreen jungle, more than 90% of which is primary forest. It borders the biodiverse Hin Namno reserve in Laos to form an impressive, continuous slab of protected habitat. More than 100 types of mammal (including 10 species of primate, tigers, elephants and the saola, a rare Asian antelope), 81 types of reptile and amphibian, and more than 300 varieties of bird have been logged in Phong Nha.

　　

Touring the park

In the past, access to the national park was limited and strictly controlled by the Vietnamese military. Access is still quite tightly controlled, for good reason (the park is still riddled with unexploded ordnance). Officially you are not allowed to hike here without a licensed tour operator. Trekking tours can be organised at hotels and tour operators in Son Trach village (note this is sometimes known as Phong Nha town). Good options include Hai's Eco Tours and Jungle Boss Trekking.

　　Most cave visits require an organised tour, notably trips into Hang En and Tu Lan, as well as the famed four-day expedition into gargantuan Son Doong (though it's worth noting the latter will set you back a cool $3000 per person). All of these trips can be booked directly with Oxalis Adventure, who are the only provider allowed to run trips into Son Doong. The Son Doong expedition in particular should be booked a long way in advance.

　　Other caves are more accessible. The eponymous Phong Nha Cave can be visited easily on a short boat trip from the jetty at Son Trach village, while Paradise Cave, at least the first kilometre of it, can be visited independently (if you have your own transport).

　　You can travel independently (on a motorbike or car) on the Ho Chi Minh Hwy or Hwy 20, which cut through the park. There is no entrance fee when entering the park. A few guesthouses in Son Trach also rent out bicycles, allowing you to explore the countryside surrounding the town at your leisure.

　　

Nearby accommodation

The Phong Nha region is changing fast. Son Trach village (also known as Phong Nha town) is the main centre, with an ATM, a rapidly mushrooming choice of accommodation and eating options, and improving transport links with other parts of central Vietnam. This is the easiest place to base yourself for exploring the park, though their are eco-farms and homestays in the back and beyond if you like your solitude. Good accommodation options in Son Trach village include Victory Road Villas, Central Backpackers Hostel and Jungle Boss Homestay.