Nearby is the War museum, where planes, helicopters and tanks are evidence of the terrible recent past. Ho Chi Minh still lies in a glass sarcophagus inside his monumental marble mausoleum.
I join the queue to file past his pale frail body, remarkably well preserved almost 50 years on, apparently due to regular maintenance in Russia.
It’s a sign of the new Vietnam, however, that the immaculately dressed sentries, once stern and threatening, now crack a smile when they wave you inside.
But Hanoi is only the start of this journey through the country. Next day I take a 100 mile trip east to Halong Bay and board a boat for an overnight cruise.
What I’ve come to see is the collection of extraordinary limestone peaks, rising from the emerald waters of the Gulf of Tonkin, like giant cathedrals.
There are more than three thousand, eroded by the wind and waves into startling shapes and topped by green vegetation. We drop anchor as the sun begins to sink below the horizon, and in the eerie silence these colossi assume their true majesty.
Back in Hanoi, I take the surprisingly comfortable overnight sleeper south.
The carriages are recent, the couchettes are clean and there’s the chance of a decent night’s sleep before arriving in time for breakfast in Hue, the imperial capital of Vietnam from 1802 until the Emperor was forced to abdicate in 1945, after the country declared independence.
The immense Imperial Citadel sits on the north bank of the Perfume River, consisting of six miles of walls, pierced by ten gateways. Inside, much is in ruins, seriously damaged by US shelling, but the temples and palaces forming the Imperial Enclosure are worth a visit.
Sadly the Emperor’s residence was razed to the ground and all that remains are low walls hiding in the undergrowth. In one corner of the site is a small museum displaying captured US artillery.
Heading further south, the train takes me to Danang on one of the most exhilarating stretches of the line, as it climbs to the Pass of the Ocean Clouds through a series of tunnels.
This is the geological divide between North and South Vietnam. Sandy beaches lie below, with hazy islands in front and misty mountains on the horizon. In his book The Great Railway Bazaar, Paul Theroux called it one of the loveliest places in the world and 40 years later it doesn’t disappoint.
It‘s 14 hours to Nha Trang through a landscape of banana trees and rice paddies with farmers in their conical hats tending water buffalo. In the carriage there’s a constant stream of railway staff dispensing mountains of rice from trolleys. I settle for a couple of beers.
Nha Tran is Vietnam’s Benidorm, clusters of high rise hotels lining the long sandy beach with more in construction. The Vietnamese are earnest holiday makers and dawn sees the shallows already packed with waders although there’s plenty of room for serious swimmers like me.
Island cruises, snorkelling and mud baths are on offer but I settle for the Po Nagar Temple Towers from the 8th century — built by the Cham people who once ruled this region.
It’s back on the rails again for the last leg of this 1,700 km journey, around eight hours to Ho Chi Minh City — or Saigon, as the locals still call it.
As I step off the train, it’s plain that the architects are aiming to compete with the likes of Singapore or Kuala Lumpur. There’s no denying its vibrancy, but the old colonial buildings like the Central Post Office and the French brick Cathedral are increasingly dwarfed by huge high rises.
In the centre, construction of the new Metro has seen yet more demolition but it’s still possible to find traces of the locations for Graham Greene’s novel The Quiet American.
He always stayed in Room 214 in the Continental Hotel — the hotel itself still exists, although the terrace outside has long gone. Next door is the still functioning Théâtre de Saigon which in Greene’s day was converted into the Lower House of the South Vietnamese National Assembly.
For those, like me, interested in the more recent past, the War Remnants museum has a clutter of military hardware in its grounds and three floors tell the grim story of the war.
The former Presidential Palace has been left as it was when the North Vietnamese tanks smashed through the gates and those same tanks still stand guard.
And a short trip out of town takes me to the Cu Chi underground tunnels where Viet Cong soldiers hid before launching their final offensive on the city. They’ve since widened a section of tunnel so Westerners can fit in but it’s still a mighty claustrophobic experience.
To make it feel more authentic, the guides, all in their late teens or early twenties, are dressed in Viet Cong uniform. I wonder aloud if they ever heard their grandparents talk about life in the tunnels but they say they died before they could ask.
Back in Saigon, sitting in the rooftop bar at the colonial Majestic Hotel, one of Graham Greene’s favourite watering holes, I watch as the sun starts to set over this modern city — and my mind returns to those demonstrations outside the US Embassy in London in the late 60s.
Who would have predicted when marching through the streets chanting “Ho, Ho, Ho Chi Minh” that after 50 years things would have turned out quite like this?
