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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.

Lao Cai is squeezed right next to the Vietnam–China border. Razed in the Chinese invasion of 1979, most of the buildings here are modern. The border crossing slammed shut during the 1979 war and only reopened in 1993. Now it’s a bustling spot fuelled by growing cross-border trade.

Ninh Binh is a good base for exploring quintessentially Vietnamese limestone scenery. Few Western tourists head here, but many Vietnamese flock to nearby sights, including the nation’s biggest pagoda and the Unesco World Heritage–listed Trang An grottoes.

Just off the Danang Beach coastal road, the Marble Mountains (Ngu Hanh Son) consist of five craggy marble outcrops topped with pagodas. Each mountain is named for the natural element it’s said to represent: Thuy Son (Water), Moc Son (Wood), Hoa Son (Fire), Kim Son (Metal or Gold) and Tho Son (Earth). The villages that have sprung up at the base of the mountains specialise in marble sculpture, though they now astutely use marble from China rather than hacking away at the mountains that bring the visitors in.

Tay Ninh town, the capital of Tay Ninh province, serves as the headquarters of one of Vietnam’s most intriguing indigenous religions, Cao Daism. The Cao Dai Great Temple at the sect’s Holy See is one of Asia's most unusual and astonishing structures. Built between 1933 and 1955, the temple is a rococo extravaganza blending the dissonant architectural motifs of a French church, a Chinese temple and an Islamic mosque.

The bustling port city of Phan Thiet is traditionally known for its nuoc mam (fish sauce), producing millions of liters of the stuff per annum. There's not much to see in town, but the riverside fishing harbor is always chock-a-block with brightly-painted boats and there are sights nearby including the Ke Ga lighthouse and Ta Cu Mountain.

Vietnam's capital races to make up for time lost to the ravages of war and a government that as recently as the 1990s kept the outside world at bay. Its streets surge with scooters vying for right of way amid the din of constantly blaring horns, and all around, layers of history reveal periods of French and Chinese occupation – offering a glimpse into the resilience of ambitious, proud Hanoians.

Once upon a time, Mui Ne was an isolated stretch of shoreline where pioneering travellers camped on the sand. Times have changed and it's now a string of beach resorts, which have fused into one long coastal strip. These resorts are, for the most part, mercifully low-rise and set amid pretty gardens by the sea. The original fishing village is still here, but tourists outnumber locals these days. There are a handful of luxury hotels (and a smattering of cheap guesthouses) but Mui Ne is mainly a midrange resort.

With limestone outcrops amid serene rice paddies, Tam Coc is best appreciated on a languorous rowing-boat ride, with the soundtrack of the river lapping against the oars.

Nowhere in Vietnam is changing as fast as Danang. For decades it had a reputation as a quiet provincial town, but big changes are ongoing. Stroll along the Han riverfront and you'll find gleaming new modernist hotels, and apartments and restaurants are emerging. Spectacular bridges now span the river, and in the north of the city, the landmark new D-City is rising from the flatlands. Venture south and the entire Danang Beach strip is booming with hotel and resort developments.