Read the passage. Choose the most suitable word to fill in the blank.
Designated a UNESCO World Heritage site ___(1)___ 2003, the remarkable Phong Nha-Ke Bang National Park contains the oldest mountains in Asia, formed approximately 400 ___(2)___ years ago. Riddled with hundreds of cave systems - many of extraordinary scale and length - and spectacular ___(3)___ rivers, Phong Nha is a speleologists’ heaven on the Earth.
The Phong Nha region is changing fast. Son Trach village (population 3000) is the main centre, with an ATM, a growing range ___(4)___ accommodation and eating options, and improving transport links with other parts of central Vietnam.
The caves are the region’s absolute highlights, but the above-ground ___(5)___ of forest trekking, the area’s war history, and rural mountain biking mean it deserves a stay of around three days.