Tran Dinh Hung travelled 5,500 miles because of his childhood dream. He came to Switzerland from his native Vietnam to work on the steam locomotives his father drove before the Vietnam War. "Every day I saw him on a steam locomotive, and heard the beautiful sound from the locomotive. So I wanted to follow him when I grew up." But, after the war, the railway into the mountains at Da Lat remained closed and the Swiss built engines languished in a jungle embrace.

Then in 1990 Hung was given the job by Vietnam Railways of helping a dozen Swiss volunteers move the derelict locos 75 miles to Ho Chi Minh City for shipment to Hamburg, and finally, Switzerland, as part of the revival of a remarkable line between Realp and Oberwald. Now retired, he was on his third visit to work on the railway when I met him last August.

Until 1982, this section of line was one of the highlights, and highest point, of the Glacier Express line between St Moritz and Zermatt. Then a nine mile "base tunnel", cut through the foot of the mountain opened, which permits year-round operation. Previously, the threat of avalanches forced closure from October to late May. Indeed, one bridge had to be dismantled every autumn to prevent it being swept away.

Ordinarily, once the new, faster, year-round route opened, the old line would have been forgotten. But a group of Swiss railway buffs thought this section was too impressive to lose. It offered the experience of climbing to the Furka Tunnel at 7,087 feet and seeing the Rhone Glacier across the valley. So they set up a body in 1983 to save it. The practical and financial challenges were so great most dismissed the idea but, section by section, the Dampfbahn Furka-Bergstrecke (DFB) was rebuilt.

The DFB reopens today for its short season, with daily trains until mid-August followed by Friday and weekend services into October.

The Rhone glacier itself has been admired since the start of Swiss tourism. In 1836, the poet Henry Longfellow described the great tongue of ice that spawned the Rhone river as "lying like a glove with its palm downwards, and the fingers crooked and closed, a gauntlet of ice which centuries ago winter threw down in defiance of the Sun". Visitors back then came by horse-drawn postbus to the hamlet of Gletsch, lost among the mountains, to walk to the glacier. Later in the 19th century, two hotels were built overlooking the glacier, the now-closed Belvedere which featured in the 1964 James Bond film Goldfinger, and the huge Glacier du Rhone Hotel of 1860, which the 1895 Baedeker travel guide book described as "first class but not quite satisfactory in some respects".

Some might say the same today, chiefly because there are no en-suite bathrooms, but I found it a delightful step back in time. The hotel's livelihood was threatened when the railway arrived in 1914, but the savvy owner insisted that in return for giving his land for the railway, midday trains would stop for lunch and evening trains would stay the night. So, a cavernous dining hall with brass chandeliers was built to augment the more intimate dining room. It still fills up with the cyclists, bikers, and motorists who converge on Gletsch from the Goms Valley and the Furka and Grimsel passes, as well as the DFB's passengers.

The DFB stations at Realp and Oberwald are a few steps from the stations of the Matterhorn Gotthard Bahn (MGB), which operates trains over the western part of the Glacier Express route between Zermatt and Disentis. A converted coach forms the cafe at Realp where most passengers take a coffee or hot chocolate before boarding the period-style carriages. First-class passengers sink into upholstered seats while, in traditional manner, second-class passengers sit on wooden slatted seats, but they are perfectly contoured for comfort.

The journey begins with a blast on a pea whistle from Gerhard Bissinger, who had come from Hamburg to act as a volunteer guard for a fortnight. The climb up the Furkareuss Valley resembles a Scottish glen in its heather-clad slopes, waterfalls, and occasional cows crop the hardy grasses. Huge boulders in the river hint of the perils of spring melt and a rock the size of a tipper truck forms one wall of a cow barn.

Such gradients can be climbed only with the help of a central rack rail, engaged by a cog on the engine which lets it claw its way up the mountain. Having to maintain the rack rail to a tolerance of one-12th of an inch is just one of the many complications facing the DFB. Another is the mile long Summit Tunnel and the expense of repairing the effect of freeze and thaw on the tunnel lining.

The western exit from the tunnel is breathtaking with roads that zig-zag up the mountain slopes to the Furka and Grimsel passes, the distant buildings of Gletsch in the valley, and the lip of the Rhone glacier. The pause at Gletsch is a chance to admire the immaculate locomotive. Nearly all of them are centenarians, painted in blue or black livery with plenty of brightly burnished steel and brass.

The final descent from Gletsch to Oberwald begins in a spiral tunnel to allow the railway to corkscrew down the mountain. It emerges to cross the Rhone and edge along the valley slope in a forest of larch and firs, with campanula and saxifrage among them. The risk of sparks igniting the undergrowth prompted the DFB to install 84 trackside sprinklers which are automatically set spinning by ascending trains. As the train approaches Oberwald, a view opens up along the broad Goms Valley, birthplace of the "king of hoteliers", Cesar Ritz.

The steam loco whispers to a halt at Oberwald station where trains head west to Brig or east through the Base Tunnel to Realp and on to Andermatt, taking just 21 minutes rather than the 130 minutes of the old route. Slow travel, but Tran Dinh Hung and thousands every year savour every minute.

Anthony Lambert.