Archaeologists working in Umm Al Quwain believe they may have located the ancient lost city of Tu'am.

It is thought the city was once the capital of a territory, on the Gulf coast of what is now the Emirates, and a pearl fishing centre famed for the quality of its gems.

So renowned was Tu'am at its peak around the sixth century that it was written of in ancient Arabic texts.

After a plague and regional tensions, the city declined and faded from memory. But now experts working at Al Sinniyah Island believe the area where a pearling village and monastery were found over the past few years is probably the location of this lost city.

Archaeologists this year found the remnants of what could be described as ancient tenements – large buildings with residential units tightly packed around narrow alleyways indicating a sophisticated settlement of thousands that was semi-urbanised and with a social class system.

Work at the site has been undertaken by the Umm Al Quwain Department of Tourism and Archaeology under the direction of its chairman, Sheikh Majid bin Saud Al Mualla, and in collaboration with local and international partners.

“This year, excavation has continued at the southern end of the pearl fishing city, with further digging in several rooms within the houses of the pearl fishing city and the Christian monastery area to better understand the layout of the buildings and document the archaeological structures,” said Rania Hussein Kannouma, acting director of the department of archaeology and heritage at the Department of Tourism and Archaeology.

“We remain committed to continuing archaeological research.”

The settlement on Al Sinniyah dates to at least the fourth century and reached its zenith during the fifth and sixth centuries. The city attracted Nestorian monks who established a Christian monastery – the second to be found in modern-day UAE – sometime between the end of the sixth century and the beginning of the seventh century.

Previously, archaeologists thought the settlement might have been a lay community for the monks. But after four seasons of work at the site, it is believed they have stumbled on something much larger.

“Our archaeological work has discovered the largest settlement by far ever found on the Gulf coast of the Emirates,” said Prof Tim Power of UAE University.

“And it's exactly the right period for the city described in the early Islamic geographical sources. It's clearly a really important place. No one has ever found it.”

Digs this winter saw archaeologists unearth the remains of densely packed buildings that were homes to scores of people. This shows the progression of the settlement that is now thought to span about 10 hectares.

First came small stone huts surrounded by discarded oyster shells. Then, because of the success of the pearl trade, the town expanded with larger homes with lavish courtyards for wealthier merchants built further away. These tenement buildings underline how droves of workers came to the settlement.

“It looks like the rich kind of flew away from the dense neighbourhood with large compounds built likely more to the north,” said Dr Michele Degli Esposti, head of the Italian Archaeological Mission in Umm Al Quwain and researcher at the Polish Academy of Sciences. “We start to see this kind of social stratification.”

Archaeologists paint a picture of a thriving but crowded city with each tenement spanning about 30 square metres. Infant mortality was high. The prevalence of tannour ovens – large clay jars turned upside down and used for fires to bake bread – meant it was probably a smoky environment.

Significant amounts of date wine jars thought to be from Iraq have been unearthed, as well as fish bones.

The residents weren't just fishing in the lagoon though.

“They were going out into deeper waters to get the larger species,” said Prof Power. “We've got quite a lot of tuna.”

Findings also show the inhabitants were connected to wider trade networks that ran through Iraq, Persia and India.

Jars inscribed with the ancient Aramaic language, the dominant language in the region before Arabic, have been found this year indicating a sophisticated level of trade.

“There seems to have been quite a cosmopolitan community, with a wide array of trade goods,” said Prof Power.

The site sits on Sinniyah Island which protects the Khor Al Beida lagoon. From the air, Sinniyah looks like a series of fingers and it is on one of these where Tu'am is believed to have been located.

Today it seems like a remote place. But the lagoon is one of largest in the region and has abundant marine resources.

“It's a really excellent location,” notes Prof Power. “You've got mangroves, which are used for cooking fuel and for possibly even building material. You've got pearl beds. There is trade to other coasts.