Archaeologists digging beneath the Palace of Westminster recently unearthed priceless historic treasures – some of which even predate Stonehenge.

In a Nov. 19 announcement, the Houses of Parliament Restoration and Renewal Delivery Authority said it had discovered relics ranging from Mesolithic flint chips to 19th-century artifacts.

The excavations were part of a three-year investigation aimed at shaping the Palace's upcoming restoration work.

The Palace of Westminster, also called the Houses of Parliament, was first used as a royal residence in the 11th century. Its oldest surviving structure is Westminster Hall, built in 1097 for William II.

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The earliest remains found during the excavation were 60 flint fragments produced during toolmaking, likely dating back to 4300 BC. The flint flakes predate Stonehenge, which began construction in 3100 BC.

The prehistoric remains were once part of Thorney Island, a sandy area near the River Thames that eventually became the heart of medieval Westminster.

"The flints were found in undisturbed sand deposits that once formed part of Thorney Island, an area where prehistoric communities are thought to have fished, hunted and gathered food," the Restoration and Renewal Delivery Authority said in its announcement.

"These rare finds offer a glimpse into early human life in what is now central London."

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Diane Abrams, the archaeology lead at the Restoration and Renewal Delivery Authority, told Fox News Digital that finding prehistoric remains in situ in central London is "incredibly rare."

"While research suggested we might find traces of early human activity on the site, I was surprised to discover direct evidence of flint tool-making dating back to around 6,000 years ago," said Abrams. 

Archaeologists also found medieval leather boot and shoe soles dating back 800 years, as well as 19th-century decorated clay tobacco pipes and a 19th-century five-pint beer jug inscribed "Geo[rge] Painter."

They also found a fragment of a 2,000-year-old ancient Roman altar that was likely repurposed, as well as a heart-shaped lead badge dating back to the Middle Ages.

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One of the most significant moments was when archaeologists unearthed the remains of Lesser Hall, a medieval building dating to 1167. First built as a royal dining space, the hall saw "key moments in Parliamentary history," officials said.

"Over the centuries, it housed the Court of Chancery, the Court of Requests, and even the House of Commons and House of Lords at different times," the Restoration and Renewal Delivery Authority said.

"This is the most significant discovery of the current archaeological investigations and provides vital insights into the layout and survival of historic structures beneath the modern Palace."

Excavators found Lesser Hall's stone wall and original foundation, which were remarkably preserved through both the Great Fire of 1834 and a World War II bomb strike.

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Abrams told Fox News Digital that the hall was one of the "most exciting and unexpected" discoveries of the excavation.

"It was unclear just how much of it would survive below the present-day courtyard and car park," she said.

"Today, its remains – and other pre-1834 structures – have been carefully recorded and even turned into 3D digital models before being reburied to protect them."

Archaeologists also spotted later repairs to the hall, including red brickwork that once separated two adjacent properties.

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"There is also a larger red brick wall which likely belonged to a cellar dividing two properties shown on plans from 1739," said Abrams.

"These details help us piece together the archaeology and history of the site to learn more about the past people who lived and worked there."

All in all, Abrams said that the discoveries "reveal a remarkable timeline of human activity on this iconic site."

"The findings will also help us to guide the design and planning for Parliament's future restoration works," she said.