For any visitor to Switzerland it won't take long to spot that every local car has a "ch" sticker on the back. All Swiss-based web site addresses end with "dot.ch", and postage stamps don't read "Switzerland", but rather "Helvetia".
It's all a reference to the tribe which peopled Switzerland 2,000 years ago.
The modern Swiss Confederation's formal name is the "Confoederatio Helvetica". The Confederation was founded in 1848 - 50 years earlier the invading French forces of Napoleon Bonaparte had declared the Helvetic Republic.
Renaissance writers describing the region that was to become modern Switzerland also used the term "Helvetian".
Traditional perceptions of the Celts see them as being confined to Europe's "Atlantic Fringe" - Ireland, Wales, Scotland, or Brittany. But the Celtic tribes were once spread across the continent, from as far east as Turkey, through what is now Slovenia and Austria, and west to France, Spain, and the British Isles.
The Helvetians were the largest of around 11 intersecting Celtic tribes living in the area that is now Switzerland. They began their slow migration from the south of modern Germany around 2,500 years ago.
This population movement picked up pace around 100 BC, as the Helvetians found themselves under pressure from Germanic tribes, descending from the north and east of Europe. They settled along the Swiss lakes and rivers, which were becoming the hub of the continent's developing trade routes, and built up a string of over 400 villages and a dozen fortified towns.
Although the Helvetians left no written records of their own, they featured in several chronicles of the period. The Greek writer Poseidonios said they were "rich in gold but peaceful people" - an interesting premonition of the modern Swiss.
Julius Caesar devoted a whole section of his "Gallic Wars" to them. Unsurprisingly, as the Roman leader was a respectful enemy of the Helvetians, whom he fought in 58BC at Geneva, after they burned their settlements and tried to move west into more peaceful lands.
Migration into Switzerland had only given them a brief respite from the advancing Germanic tribes, which were continuing their move south. After their defeat at Geneva the Helvetians were forced back into the conflict zone by the Romans, and their territory became a province of the Empire in 15BC.
During the period of benign imperialism which followed, Rome's cultural influence on the region and its people was profound. The Helvetians adopted Latin, their larger settlements turned into major Roman urban centres, and the road network was expanded to complement the Celts' river routes.
Roman rule lasted until the Helvetian province, after a slow infiltration, finally fell under the control of the Germanic Burgundians and Alamans in around 400AD. But the Helvetian Celts remained, living side by side with the newcomers.
Traces of the Latinised Helvetians survive in modern Switzerland. The country's language divide is an illustration.
The Alamans who settled in the east retained their Germanic dialects. The French-language term for German-speaking Switzerland remains "la Suisse alémanique".
But the Burgundians who colonised the west adopted the Latin dialects of the Helvetians. French-speaking Switzerland is thus a cultural footprint of the Celts.
The German names of Cantons Valais - "Wallis" - and Vaud - "Waadt" - also refer to the Helvetians. Like "Wales", both are originally terms used by the Germanic tribes to describe "strangers", the Celts they encountered.
Felix Müller, the deputy director of Berne's Historical Museum, is also one of Switzerland's leading experts on the Celts.
"There's plenty of evidence still around us left by the Helvetians," he says. "For example, modern-day Avenches, with its impressive amphitheatre, was a Romanised Helvetian settlement called Aventicum."
"Yverdon is an entirely Celtic name, too. People are sometimes surprised to learn that Berne was an important Celtic settlement - sited not on the bend of the River Aare where the medieval city was established, but on the Enge, a steep peninsula about four kilometres north."
Müller has even found evidence of settlements burned by the Helvetians, before they set off for Geneva in 58BC. Just above Avenches is the site of a smaller fortress, where archaeologists have discovered a buried layer of charcoal covering the remains.
The country's Celtic past still arouses growing interest in Switzerland. An exhibition on Celtic jewellery organised by Müller in Berne earlier this year attracted a huge number of visitors.
In Corbeyrier, a small mountain village in Canton Vaud, the local residents have made something of a feature of their interest in the past. In order to raise the place's profile, they decided in 1996 to start a Celtic festival.
Local teacher and amateur historian, Max-Olivier Bournoud, believes Corbeyrier lay on a major trade route, bringing tin from Cornwall in Britain down to Greece. He has also identified a number of Celtic sites and place-names in the region.
"Quite a few people in Switzerland start out with an interest in Celtic music - say from Ireland or Brittany - and then want to learn more about the Swiss past. I think it's because of globalisation, since people feel an unconscious need to lock on to their roots, but I don't think this means you have to shut out the rest of the world," said Bournoud.
Some Swiss take their interest in the Celtic past a step further. Solas is a practising druid from Canton Vaud. She says she began reading about Celtic druidism a few years ago, and decided she liked the philosophy.
"It's not so much a religion as a way of life. Our Helvetian ancestors are our roots, and I feel strongly connected to them", she said.
Müller thinks one of the things that people find so attractive about the Celts is the element of the unknown. "Because they didn't leave written records, but were written about, and because we have only a few archaeological vestiges, we find the Helvetians mysterious and adventurous," he said.
by Jonathan Fowler