No one disputes that Oc Eo is a site of great archaelogical value. Vietnam this week named it a "national relic". But was it also the place where ancient Romans and Khmers met?

In 2nd century AD Egypt, the legendary Greco-Roman scientist Claudius Ptolemy put the extent of the known world onto paper. From his home in Alexandria, he gathered reports from sailors who had made perilous journeys to India and possibly beyond. Though details were sparse, a voyager named Alexander described a distant port called Kattigara on the Sinus Magna (Great Gulf) to the east of the Golden Chersonese peninsula – widely considered to be mainland Malaysia.

Halfway across the world around the same time, the bustling seaport Oc Eo was part of the flourishing Funan Kingdom, the earliest known pre-Angkorian civilisation and origin of the earliest Khmer-language inscriptions.

Located in modern Vietnam’s An Giang province near the Cambodian border, Oc Eo was on Monday declared a “national relic” by the Vietnamese government. Vuong Binh Thanh, chairman of the People’s Committee of An Giang, reportedly told onlookers that it was essential to preserve the 450-hectare site for the sake of tourism and academia alike.

Excavation at Oc Eo suggests it was major centre for international maritime trade. Unearthed jewellery, pottery statues, coins and gold pieces – including depictions of Hindu deities and Sanskrit inscriptions – indicate busy trade with the Indian subcontinent.

Most curious, however, are the 2nd century AD Roman coins, found by French archaeologist Louis Malleret, who is credited with discovering the archaeological site in 1942.

While certainly one of Vietnam’s most important archaeological sites, could Oc Eo actually be Ptolemy’s Kattigara? And is it possible that Roman mariners could have travelled there and encountered Cambodia’s ancient ancestors?

While the idea seems fanciful, it’s not new. The notion was even suggested by the late George Coedes, arguably the most influential historian of ancient Southeast Asia.

“Funan may even have been the terminus of voyages from the Eastern Mediterranean, if it is the case that the Kattigara mentioned by Ptolemy was situated on the western coast of Indochina on the Gulf of Siam,” he wrote in a 1964 article from the Journal of Southeast Asian History.

The possibility seems less farfetched in light of the well-documented direct maritime trade between Rome and western India. According to Periplus of the Erythraean Sea, a Greco-Roman manuscript most likely written in the middle of the 1st century AD, the Greek navigator and merchant Hippalus was the first to discover the monsoon winds that could take a ship from the Roman provinces along the Red Sea to India without following the dangerous coastal route.

Spices, Chinese silk, fruit and even wild animals were traded for Roman coins, which have been excavated along the western Indian coast. Silk had become so popular by the late 1st century AD that Pliny the Elder even complained about Rome’s lust for the fabric.

“At the smallest reckoning, 100 million sesterces [of gold] is the sum which every year India, the silk-growing country of northern China, and the Arabian peninsula take from our Empire,” Pliney wrote.

But while the western Indian Ocean sea route was well documented by contemporaries, Roman theories of what lay east were far sketchier. Rome and China knew of each other through trade intermediaries in South and Central Asia, who jealously guarded their knowledge to retain their lucrative middlemen status. The Romans knew China as Seres, the land of silk, while China knew Rome as Da Qin, which literally translates to “Great Qin” in reference to the Qin Dynasty.

A single, uncorroborated account of Romans in Southeast Asia can be found in the Hou Hanshu, an official Chinese history compiled by the courts of the Liu Song dynasty in the 5th century AD.

The document states that Roman sailors arrived in 166 AD at Rinan – located in modern day central Vietnam – with gifts of ivory and tortoise shells for the Chinese who then ruled the area. The meeting, reads the document, was the first instance of direct communication between the empires.

But it has yet to be demonstrated whether Romans directly met the peoples of East and Southeast Asia or only picked up scattered titbits and artefacts via intermediaries.

Kattigara, said professor Miriam Stark, a specialist in the Funan period at the University of Hawaii, could have been as far south as Sumatra according to modern peer-reviewed scholarship on the subject.

“I can’t say that Oc Eo (or even the Mekong delta more generally) was the Kattigara that Ptolemy describes,” said Stark in an email, adding that archeologists have yet to find firm evidence confirming Kattigara’s location.

Concordance with multiple sources, she said, was also lacking, and the Roman coins unearthed at Oc Eo were of dubious provenance because Malleret mostly purchased them from locals rather than excavating them himself.

However, Kasper Hanus and Emila Smagur, both PhD candidates at Poland’s Jagiellonian University, argue in a yet-to-be released research paper that Oc Eo is the “most probable” location of Kattigara.

Hanus, who is also a research affiliate at the University of Sydney, agreed that the lack of evidence meant that committing to any particular theory for the location of Kattigara was “gambling”.

But he cited Oc Eo’s importance in contemporary maritime trade along the Gulf of Thailand, the discovered Roman relics and Ptolemy’s description as compelling evidence in favour of the theory.

“What we can say for sure is that Oc Eo was an important trade site along the maritime Silk Road that linked China, India and the Mediterranean world, and the concentration of overseas goods suggests its vital role in intercontinental commerce,” said Hanus, adding that more written evidence from the period was needed.

“In general, the late prehistory of mainland Southeast Asia is developing very fast, and every year we witness new discoveries, so I suggest to have our minds open, and verify and change our ideas as the new evidence arrives.”