An ancient Roman basilica has been discovered below London’s financial district

Archaeologists in London have uncovered a section of Roman masonry that belongs to a nearly 2,000-year-old town hall, in what historians say is one of the most significant discoveries in the British capital since an ancient amphitheater was unearthed in the 1980s.

Developers working to tear down a 90-year-old commercial building in the heart of the city’s financial district — officially known as the City of London, or “Square Mile” — worked with specialists from a team at the Museum of London Archaeology to reveal extensive masonry that once formed part of a basilica beside the forum of the Roman settlement known as Londinium. The settlement thrived for a few hundred years until its decline some 16 centuries ago. (Archaeologists are required to be involved in new British developments when there is concern about heritage, and were particularly aware of this area’s potential historical significance).

In the basement of that commercial building on Gracechurch Street, surrounded by high-rise towers filled with financial and insurance firms, archaeologists began excavating large, exploratory pits two years ago until stone walls several feet thick and dozens of feet long were exposed.

“In one trench, we hit a massive piece of masonry — it was about three or four feet wide,” says Sophie Jackson, director of developer services at the Museum of London Archaeology. “We extended the pit, and it kept on going. So basically, we got a huge piece of Roman wall, which represents part of the structure for the nave of this basilica, the central part of this town hall.”

Jackson says the Roman building known as a basilica was a crucial component of any sizeable Roman settlement of that era, much like an amphitheater, public bath or the fortified walls that ringed them.

“It’s the sort of heart of of any significant Roman town,” according to Jackson. “It’s where the administrative center [is], it’s where the law courts are, it’s where the magistrates sit — it’s where all the big decisions are made. But it’s also a place where merchants would come and do business.”

What Jackson and other archaeologists and historians say is so extraordinary about the find is that the area has remained a commercial center for hundreds of years and been extensively rebuilt many times over since the Middle Ages.

“For something so important to the history of London to survive so much development over so many centuries is really remarkable,” says Jane Sidell, the principal inspector for ancient monuments at Historic England, a public agency that advises the U.K. government on sites of national and historical significance.

Sidell says she is most excited about the promise made by the new building’s developer, Hertshten Properties Limited, to place some of the archaeological items on public display, as Michael Bloomberg did nearby with a Roman temple that was discovered under what became his company’s London headquarters. It is the kind of historically sympathetic construction that she says was long missing during London’s boom years of the 20th century.

“You can read all you like, you can watch Gladiator at the cinema, but when you actually physically come face to face with something that’s been there,” explains Sidell, “that connection with a nearly 2,000-year-old legacy is amazing.”

The basilica was built around 80 C.E., the archaeological team estimates, and was discovered on a site that was known to have formed part of the city’s forum area, ever since discoveries in the 19th century helped experts sketch out a rough plan of the earlier Roman town center.

At the time of the basilica’s construction, Londinium’s future had been recently in doubt as a major settlement, after it was sacked by a revolt against Roman rule several years earlier.

But with a population of perhaps 40,000 residents, according to MOLA’s Jackson, the decision to build such a sizeable basilica, almost 40 feet tall, represented a vote of confidence in the city’s future.

“It was a really high building, and nobody would have seen anything like this before in Britain,” she says. “It was designed to impress and — perhaps — intimidate the local population.”