As the story goes, in 53 BC, a Roman legion based in what is now Iran lost its commanding officer. They worked as mercenaries, travelling eastward, until they were captured by the Chinese some 17 years later. They eventually settled in China in what is now the village of Liqian. To this day, their descendants have distinctly European features.
Whether it's true is up to the DNA test to prove or disprove. But as a story, it's pure gold.
From the Sydney Morning Herald story:
The town's link with Rome was first suggested by a professor of Chinese history at Oxford in the 1950s. Homer Dubs pulled together stories from the official histories, which said Liqian was founded by soldiers captured in a war between the Chinese and the Huns in 36BC, and the legend of the missing army of Marcus Crassus, a Roman general.
In 53BC Crassus was defeated by the Parthians, an empire occupying what is now Iran, putting an end to Rome's eastward expansion.
But stories persisted that 145 Romans were taken captive and wandered the region for years. Professor Dubs theorised that they made their way eastwards as a mercenary troop, which was how a troop "with a fish-scale formation" came to be captured by the Chinese 17 years later.
He said the "fish-scale formation" was a reference to the Roman "tortoise", a phalanx protected by shields on all sides and from above.
Certainly great material for a movie or a mini-series.