WE BEGIN our trek early in the morning, eight of us, still a little sleepy and anxious about whether our muscles will endure four arduous days. After spending the night at a guesthouse in the Skaftafell National Park, we are taken by truck and dropped further up the coast, on a fine black-sand beach peppered with melting icebergs.

As soon as we start walking, a fierce wind blows up off the Atlantic and blasts cold air in our faces, forcing us into single file, each trying to find shelter behind the other as we progress slowly. We can barely see as the mist closes in on us, so we just watch our feet, tramping over the spongy green moss that covers the uneven ground. The mist is actually a rainsquall which then hits us head on, and the group stops briefly as we rush to pull on our waterproof layers.

Less than a mile into the trek we are all quietly wondering whether the whole idea of a walking trip in Iceland was really such a good idea. "I'd rather be in Largs," I hear someone mutter.

And then a little miracle happens. The rain eases and the mist lifts away. There is no sudden ray of sunshine, just a soft, golden hue that gently warms. It gradually occurs to me that I can now lift my head and I notice my companions are doing the same, staring in awed silence at the landscape.

Down the slope and to the right is a broad, shimmering lake filled with a marvellous array of icebergs. Those that have been facing the light are matte white, while others are a soft, translucent blue. Eventually I realise that the opposite bank of the lake is not land at all, but the face of a great glacier, stretching up many hundreds of metres towards two towering volcanic peaks. The water is the giant puddle left behind as the ice retreats.

A shout breaks the stunned silence as someone points out the shape of a frolicking seal. Then another, and another: a whole family lounging on the ice like holidaymakers on the beach, staring at us with curiosity. Framing this whole scene is the perfect, sweeping arc of a full rainbow, both ends touching the water.

The glacier itself is gigantic, with enormous tongues of ice piling down from the massif towards the sea. It cuts directly across our path, which means we have to cross it the next day. Glaciers look and feel remarkably solid - covered in a fine layer of gritty sediment, they have the appearance of dark grey rock - but for all their bulk they are constantly on the move, flowing down the mountain at a rate of as much as 200m a year, while their outer edge is simultaneously retreating as the planet steadily warms. The result is an uneven, often jagged surface that is not always stable. Attempting a crossing without a guide is not recommended. We strap our crampons to our boots and clasp the ice-axes supplied to us for the day, obediently following closely in the footsteps of Hjolli, our local mountain guide.

For a long time, no one wanted to go to Iceland at all. This distant Atlantic island, on the cusp of the Arctic Circle, can be cursed with furious volcanic eruptions and the weather is often downright awful. But now it is this rugged landscape that is proving so attractive for tourists looking for an active break.

One of the first recorded settlements of Iceland was in the 9th century, when Norseman Floki Vilgerdarson loaded a longboat with his family and herd and sailed across the North Sea in search of new land and a better life. The family lasted less than a year: winter was so severe that the crops failed and virtually none of the livestock survived. Vilgerdarson climbed a peak, hoping for a glimpse of milder pastures and sheltered valleys inland, but all he encountered was the giant glacier. He sailed back to Norway impoverished and disillusioned, never to return to the place he had named Iceland.

Finally, some permanent settlers arrived, most choosing the more accommodating south west, where most of the population still lives. Centuries later, when foreigners first started arriving in large numbers (primarily British and American soldiers, after the outbreak of the second world war, and then tourists in the last two decades) there was palpable disappointment. The notorious reputation of Iceland's geology and climate had become a source of fascination, but instead of ice they were faced by a remarkably green and mild place, where the temperatures often stay above freezing even in mid-winter. Wet-and-windy-land seemed a more appropriate name. Even today, with many travellers only stopping off for a soak in the thermal waters of the Blue Lagoon, or a short stay in Reykjavik, the sentiment is often the same.

For the true Icelandic wilderness experience it is necessary to travel into the huge, uninhabited interior of the country. To the north is Europe's highest waterfall and a famous geyser, but perhaps the most spectacular experience is a visit to the Oraefajokull massif, one of the most extensive glaciers on the planet which occupies virtually all of southeast Iceland. This is where Vilgerdarson landed more than 1000 years ago, and where our group finds itself now.

The sky clears as the last of the daylight drifts over the horizon and we huddle in the large tent at the centre of our camp, warming ourselves with alcohol and conversation while the local guides offer tall tales and bizarre stories about their charmingly idiosyncratic country. The trip ends with a journey back to Reykjavik, where we are all delighted to shower and shave; cleaning away the week's exertions. Aching muscles are soon forgotten in the jovial capital city, but the desolate beauty of this great, empty island will stay with us for far, far longer.

HOW TO GET THERE Icelandair (www.icelandair.co.uk) flies to Reykjavik from Glasgow from £99 return.

FURTHER INFORMATION Discover the World offers city breaks in Reykjavik from Glasgow from £330 per person. Glacier day excursions are available for £125 per person (www.discover-the-world.co.uk; www.arcticexperience.co.uk/iceland).

For longer expeditions, try www.mountainguide.is CARBON FOOTPRINT About 0.38 tonnes of CO2 per passenger on a return flight.