A heavily corroded bronze coin bearing the unmistakable face of Roman Emperor Constantine has been discovered four metres beneath the Notre-Dame Cathedral courtyard, anchoring a stunning timeline that stretches from antiquity to the Middle Ages.


The historic artifact, initially pulled from the mud as a blackened, unrecognisable disc, was successfully identified using advanced laboratory X-ray imaging. The breakthrough provides a direct physical link between Europe’s most famous Gothic cathedral and the ancient Gallo-Roman city of Lutetia.


THE BREAKTHROUGH: X-RAYS UNLOCK THE ROMAN TIMELINE

Archaeologists from the Pôle archéologique de la Ville de Paris, including researcher Valentine Breloux, have spent months excavating the cathedral’s parvis (front square) [Breloux Valentine Paris Nanterre University Profile]. For the scientific team, the 4th-century coin is far more than a museum piece—it is a vital geological clock.

  • The Invisible Emperor: Centuries of soil acidity left the coin entirely encrusted in rust [CBS News]. Conservation expert Lucie Altenburg utilised X-ray technology to look beneath the corrosion, revealing the profile of Constantine the Great.
  • Dating the Earth: Finding currency from a known ruler establishes a precise chronological marker for the dig [CBS News]. It confirms the exact depth of the late-Roman stratum before the site transitioned into a medieval urban hub.
  • A Fortress of Recycled Stone: The excavations show that as the Roman Empire collapsed, frantic citizens tore down imperial monuments, flipping the stone blocks upside down to build a defensive wall around the island (Île de la Cité)

HISTORICAL CONTEXT: CONSTANTINE’S FRONTIER COIN

The presence of Constantine’s currency beneath Notre-Dame highlights the strategic importance of early Paris within the Roman Empire.

  • The Emperor: Reigning from 306 to 337 AD, Constantine the Great fundamentally altered Western history by legalising Christianity and moving the imperial capital eastward.
  • The Military Outpost: During the 4th century, Constantine’s imperial family used northern Gaul (modern-day France) as a critical military staging ground to defend Rome’s borders against Germanic tribes.
  • The Soldier’s Pay: Millions of these bronze coins were minted and distributed across western outposts to pay frontier soldiers and fund rapid fortification projects, meaning this specific coin was likely dropped by a Roman soldier or merchant.

BEYOND ANTIQUITY: MEDIEVAL SECRETS UNCOVERED

The Roman coin is only one layer of a complex historical “lasagna” being peeled back by researchers. Just above the Roman ruins, Valentine Breloux’s team has targeted ancient medieval household rubbish and latrine pits.

Because the centuries of soft organic waste cushioned falling objects, archaeologists have recovered miraculously intact medieval ceramic jugs, plates, and cups. Most enticing to historians are a series of pottery shards featuring mysterious, faint reddish inscriptions painted on the inside. Experts are currently working to decipher these ancient scripts, which could unlock details about daily domestic life in medieval Paris.

SOURCE:  https://greekcitytimes.com/2026/06/02/notre-dame-roman-coin-emperor-constantine-discovery/