A priceless gold bust of emperor-philosopher Marcus Aurelius, one of Europe's greatest Roman relics, has returned to this quiet Swiss town where it was found in an ancient sewer 67 years ago.

One of only three golden imperial busts to have survived across the vast territories of Rome's empire, the excitement surrounding its discovery in 1939 was so great that residents who witnessed it still talk about it today.

Now, they are thrilled it has returned home, albeit only for the summer and under tight security at Avenches' Roman Museum.

"It is wonderful to have it here where people can see it in the context of our town and its history, and not hidden away from public view," said museum director Anne Hochuli-Gysel.

After its discovery, the bust was whisked off to bank vaults for safe-keeping and has only been occasionally loaned for major foreign and Swiss exhibitions, largely remaining locked away although people in Avenches have always regarded it as theirs.

The reappearance in the town of the pensive 22-carat image -- a power symbol carried at the head of legionary columns -- of the emperor who ruled from 161 to 180 AD has served to highlight the mysteries that still surround it.

Where was it made? How did it come to a town several days' march from the nearest legion garrison? Why was it in a sewer? And why did whoever put it there -- probably to keep it safe from "barbarian" attack -- never recover it?

The bust, displayed behind red plush curtains not far from the plaster copy that has stood in its stead for decades, has excited the local imagination.

Schoolchildren and students selling programs at the opera festival and youths selling coffee from portable dispensers on their backs point visitors to the tower.

"The bust has become a symbol of our town," said one official. "Having it in the museum, even if only for a few months, has given people a new sense of pride in their past."

ANCIENT CAPITAL

A collection of wooden huts in the middle of a fertile plain in AD 15 when the Romans conquered what is now central Switzerland, as Aventicum the town quickly became capital of the rich province of Helvetia.

Standing on key military and trade routes linking Italy and the Lake Geneva region to the south with legionary outposts on the German frontiers in the north, it flourished to number 20,000 inhabitants 200-300 years later.

Today, Avenches is little more than a village of some 2,600 people just on the francophone side of the "rostigraben" border dividing French- and German-speaking Switzerland.

Older residents who recall the discovery of the unscathed bust speak of the general excitement at the time, with people flocking into the town from all over Switzerland to see it in a makeshift case on a table in the excavators' workshop.

"I got to the dig just a few minutes after they had found it," said 73-year-old Eugene Ruffy, who was 6 at the time. "In 1939 life was pretty difficult for us and the discovery of something made of gold was like a fairy tale.

"When I got home and told my parents, they were so surprised that they even asked if I had imagined it."

The bust was only displayed in Avenches for about a week.

Declared the property of the Canton of Vaud, to which Avenches belongs, it was taken away to be put briefly on show in Zurich at the Swiss National Exhibition of 1939 and then sent to the Vaud cantonal bank in Lausanne.

PRICELESS

Some two-thirds natural size, the bust -- whose pure gold content would today fetch scarcely more than 26,000 euros ($40,000) but in Roman days would have paid the wages of 24 legionaries for a year -- is beyond price, experts say.

Some say it would have come to Aventicum as a gift to his home town from a Romanized Helvetian officer and then became an object of worship in a temple to Marcus Aurelius.

Archeologists who first examined the bust in 1939 thought it was his predecessor and patron Antoninus Pius.

But experts today, comparing it with his image on stone sculptures and Roman coins showing the same wide-set eyes, hair style and curling beard, have no doubt it is the author of "Meditations."

Local historians say the bust was probably hidden in the sewer -- perhaps by a sanctuary priest -- at a time of danger from rebellious tribes who roamed the region in the 4th century. The knowledge of its whereabouts was lost when its keeper died.

In late autumn, it will go back to the Lausanne vault.

"There is no barbarian threat now, but perhaps it is best to keep it safe. After all, no one saw it for all those years it was in the sewer," said one historian with a sigh.