For the connoisseur of ancient art, 6 rue Verdaine in Geneva's old town is a jewel to behold. Set in its windows, like pearls in an oyster, are an elegant Attic red figure krater attributed to a 5th-century BC painter, an Etruscan pouring vessel and an array of vases.
Enter the plush showroom and the antiquities get better. Just in from the collection of an anonymous Swiss gentleman is a rare, 4th-century AD portrait of Helena, the mother of Constantine, the founder of Byzantium. The bronze bust, though severe of expression, is the showpiece of Phoenix Ancient Art - and comes with a £1.2m price tag. "Great-quality antiquities are a great investment," says Ali Aboutaam, the gallery's Lebanese proprietor. "They're a fraction of the price of, say, buying a Picasso."
In a world where cynicism and forgeries prevail, Mr Aboutaam insists no piece is purchased without being checked first, through the vendor, Interpol and various publications. "We're against dealing in illegally excavated antiquities and we don't support that market at all."
But in the increasingly sophisticated international art market, even items sold openly and legally with apparent provenance can cause controversy. Six years ago Phoenix Ancient Art sold a 3,200-year old mummy mask to the St Louis Art Museum that Egypt claims was stolen from the Cairo Museum, although Mr Aboutaam says "there is no evidence to support" the accusations.
In 2004 a life-size bronze sculpture of Apollo Sauroktonos stood in the showroom before it was sold for an undisclosed amount to the Cleveland Museum of Art. Carved by Praxiteles, the master artist, the work is seen as the finest piece of classical sculpture purchased by a north American museum since the second world war.
"[We] acquired the Apollo ... after over a year of extensive research. An international team of specialists thoroughly considered the acquisition from legal, art-historical,and technical perspectives, including laboratory testing. An emphasis was placed on research into its history," says a spokeswoman, Donna Brock, adding that the museum remains confident about its decision.
'We stand by its provenance'
Mr Aboutaam also says the statue was bought in good faith. "We stand by its provenance." An account of the statue's ownership history released at the time of the acquisition by the Cleveland, and endorsed by Phoenix Ancient Art, says the monumental bronze was "a part of a private estate" in the former East Germany until it was rediscovered "in pieces" in 1990. The family who reclaimed the estate upon reunification, sold the work in 1994 to unnamed persons before it was acquired by Phoenix Ancient Art.
But, this month, as Greece stepped up its campaign against the illegal antiquities trade and announced it would demand the repatriation of hundreds of looted works, the statue again became the focus of scrutiny. Mr Aboutaam may have exercised due diligence when he bought the masterpiece but authorities in Athens believe that before it entered his showroom it was passed through a chain of traffickers on the underground market. "We're investigating this statue and whether it was stolen very closely," says Giorgos Gligoris, who heads Greece's art squad. "We believe that it was, that it's a typical case of antiquities theft. We're in the process of studying photographs. The Italians, we have learned, may be claiming it and so may we. Our information from informers is that it was found in the Ionian Sea and then passed on, through I don't know how many hands, before being sold."
From his sixth-floor office in the Orwellian building that is the Athens police headquarters, the detective oversees a web of informants in and outside Greece. Among his targets is the freeport in Geneva where the sellers of museum-quality pieces often store their stock and where specialists believe the illicit journey of plundered art into some of the world's greatest museums often begins.
"We have people in Geneva because it seems that containers always pass through the freeport," he says. "Smugglers like Switzerland, with its flexible laws and good location, but they can see we're closing in on them."
In 1997 Swiss police found and seized 10,000 antiquities, many still covered with dirt, all bearing the stamps of well-known auction houses, hidden in four of the huge grey warehouses that girdle Geneva's freeport transit area.
Home to an estimated 34,000 archaeological sites, Greece is viewed as Europe's biggest open-air museum. Along with Italy, it has attracted tomb raiders since before its foundation as a nation state in 1830.
But Athens is toughening its stance, homing in on the dealers, curators and collectors that are the source of demand. This month the J Paul Getty Museum in Los Angeles agreed to yield ownership of two pieces that Greece had long claimed.
"All these illicit digs have resulted in an extraordinary loss to our heritage," says Maria Pantou, the director of the department of museums at the Greek culture ministry. "Every time an object is removed from the ground [illegally] it immediately loses 85% of its worth, even if it is a masterpiece," she said. "Unless something is documented, it's very hard to prove from where it came."
As supplies have dwindled and demand has grown traffickers have become ever more expert. Greece's network of dealers and smugglers have been forced to look further afield.
After the Balkans, where illegal excavations have escalated alarmingly, thieves have turned their attention to the Middle East and the far east - especially the estimated 11,000 precious artefacts still missing after the notorious plundering of the Baghdad Museum in April 2003.
"Unlike Italy, in Greece there's not a lot of stuff left because smugglers have been around for hundreds of years," says Nikolas Zirganos, an Athenian journalist who has researched the subject extensively. "These rings have begun to understand that both Athens and Rome are determined to clamp down on the trade so now they're expanding to places like Babylon and Cambodia."
· The illicit trade in antiquities world-wide is worth about $2bn (£1.1bn). Tomb-robbing is said to be the world's second oldest profession
· During the past 20 years, between 65% and 90% of antiquities put on sale on the London art market were of unknown provenance and were probably illegally excavated. More than £3m worth of antiquities are traded in London auction houses every year
· John D Cooney, a former curator of ancient art at Cleveland Museum, announced in 1970 that 95% of all antiquities in the US had been smuggled