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Northern Vietnam's most appealing city has a distinctly laid-back air with its tree-lined boulevards host to a bundle of colonial-era buildings. Caffeine-aficionado heaven, the central area buzzes with dinky cafes where tables spill out onto the pavements – perfect for people watching.

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.

Cat Tien comprises an amazingly biodiverse area of lowland tropical rainforest. The 72,000-hectare park is one of the outstanding natural treasures in Vietnam, a true jungle, and the hiking, mountain biking and birdwatching here are the best in the south of the country. At weekends and public holidays it gets busy with domestic tourists – it's worth calling ahead to book the most popular excursions.

Quang Ngai city is something of an overgrown village, so most visitors only drop by for a spot of grazing at lunchtime. The few travelers who venture here for longer usually do so to pay their respects to the victims of the most famous atrocity of the American War at nearby Son My.

Ha Tien may be part of the Mekong Delta, but lying on the Gulf of Thailand it feels a world away from the rice fields and rivers that typify the region. There are dramatic limestone formations peppering the area, which are home to a network of caves, some of which have been turned into temples. Plantations of pepper trees cling to the hillsides. On a clear day, Phu Quoc Island is easily visible to the west.

A popular weekend escape from HCMC, Vung Tau rocks at weekends when beach-starved locals and expats descend in numbers, but it is relatively quiet during the week. The city enjoys a spectacular location on a peninsula, with ocean on three sides; the light and sea air make it a refreshing break from sultry Saigon.

Ancient Hanoi preserves the best parts of French and Chinese culture and architecture, and weaves it all into the modern world with youthful Vietnamese verve. If that gets too boisterous, two nearby national parks offer clean mountain air, rare plant life and animal-spotting opportunities. At Tam Dao Hill Station the weather is cool year round, while Ba Vi National Park offers hiking through atmospheric mist to a mountaintop temple.

Sleepy Bac Ha wakes up for the riot of color and commerce that is its Sunday market, when the lanes fill with villagers who flock in from the hills and valleys. Once the barter, buy and sell is done and the day-tripper tourist buses from Sapa have left, the town rolls over and goes back to bed for the rest of the week.

Rugged, craggy and jungle-clad Cat Ba, the largest island in Halong Bay, has experienced a tourism surge in recent years. The central hub of Cat Ba Town is now framed by a chain of low-rise concrete hotels along its once-lovely bay, but the rest of the island is largely untouched and as wild as ever. With idyllic Lan Ha Bay just offshore, you'll soon overlook Cat Ba Town's overdevelopment.

Gateway to the Mekong Delta, My Tho is the capital of Tien Giang province and an important market town – although for the famous floating markets, you’ll need to continue on to Can Tho.