The top of Hai Van Pass, which is the frontier between Thua Thien-Hue province and Da Nang city, still boasts the historic brick Hai Van Gate, built under the Tran dynasty in 1470, when King Tran Nhan Tong proclaimed that Hai Van was ‘the most marvelous wonder'.

The pass, popular for motorbike drivers since the Hai Van Tunnel became operational in 2005, is quiet and safe for off-road bikers and tourists. But the bends on the road still challenge drivers with a 15 percent uphill slope.

Nguyen Dong, a member of the Honda 67 (T-bone SS50 motorbike) Club in Da Nang, started his off-road tour to the Hai Van Pass on a hot day, as he said it would provide the best photos.

His 10-member group, comprising different kinds of motorbikes, began the tour in the morning.

"It's really a challenge for young drivers. Scooterists find it a bit difficult as they have to slow down at bends for just a moment, and then suddenly press the accelerator to complete the curve.

"The pass road has been widened and upgraded over the past decades for safe and easy off-road driving," he said.

Traffic mirrors, set at all bends in the road, warn drivers about traffic coming from the opposite direction, helping them to control their uphill speed.

"New drivers can find it thrilling when they face the first curve, just after the railway crossroad. It's quite narrow and the driver has to slow down and shift to the first gear," he said, adding that most motorbikes have a four-gear box. 

He said experienced drivers preferred sporty bikes than scooters or other motorbike brands because the drivers could increase their speed by changing gears and using the clutch easily.

The group made some stops on the way to take photos of falls or beaches at the base of the mountains.

Nguyen Trong Hoa prefers using his vintage style scooter, Vespa.

"It's not as strong as the other new bikes, but I prefer to ride it to go to Hai Van Pass just because I like the vintage style," Hoa said.

Le Hai Son, a mechanic, said: "We often check our bikes for safe travel. I also warn team members after driving a good distance along the snaking 24km road about safety." 

The group arrived at the top of Hai Van Pass after going through four tough bends and dozens of tortuous roads in 45 minutes.

The top of the mountain still has an octagonal bunker, built by the French in 1826, and an ancient brick gate.

"The gate is in good condition and has an ancient design. It's the only ancient architectural structure that has survived since 1047, before being restored in 1826," Da Nang-born Son said.

A 1,000sq.m area was constructed as a rest stop for motorbikes and caravan tours on top of the mountain, along with souvenir and coffee shops. 

"Stone sculptures, souvenirs and fast food shops were built for tourists. But the brick gate is always a must-visit," Son said. 

The mountain top is always covered by clouds, and often has a cool temperature of about 17 degrees Celsius. Drivers can face difficulties due to fog on rainy days and also late in the evening. 

"Hot coffee warms you up and the smiles and hospitality of shop assistants make the atmosphere more friendly and exciting," Hoa said.

The group continued their trip after a 20-minute break. 

The downhill trip was also a challenge for the group as the brake systems almost gave up.

"There are four tough curves and some winding bends, but I had to press the front and rear brakes to slow down the downhill speed," Hoa said.

"I even shifted the gear down to second or first gear for tough bends. Younger drivers made their brake systems get too hot, and had to make more stops," he said. 

After the last bend, a beautiful sandy area appears in a small fishing village in Lang Co town. It is a favourite rest stop of tourists. 

Lang Co offers many beaches and lagoons - An Lap and Tam Giang - Cau Hai - for holiday makers.

Tourists can reach the top of the pass and return to find a rest stop at the base of the mountain in Da Nang. 

The Mekong Hai Van rest stop at the base of the mountain is often a stop for trans - Viet Nam travellers, and for camping as well as a rendezvous point for weekend team-building activities.

It's also the first stop just 2km after the Hai Van Tunnel - the longest tunnel in ASEAN, connecting Thua Thien-Hue province and Da Nang city - for people travelling a long distance by bus or motorbikes.

The main two-storey building, with a 200m - diameter conical structure, has souvenir shops and food corners for visitors.

Pham Van Tuan, the manager of the Mekong Hai Van restaurant, said three restaurants with 2,500 seats offered a large and relaxed space for travellers. 

Tuan said the rest stop offered a panoramic view of the mountains and beaches.