It has been nearly four years since a fire damaged Paris’ iconic Notre Dame Cathedral, but as repairs continue ahead of the 2024 reopening, the landmark is giving historians and archeologists a glimpse into how the cathedral was constructed.

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The cathedral was damaged in a massive fire on April 15, 2019. The spire collapsed in the blaze that destroyed the roof of the church, The Associated Press reported.

That spire will be reconstructed, with it starting to appear this year, and the cathedral is scheduled to reopen in December 2024 for both tourists and religious services, the AP reported.

“The return of the spire in Paris’ sky will in my opinion be the symbol that we are winning the battle of Notre Dame,” Gen. Jean-Louis Georgelin told the AP earlier this month.

While people await the return of the spire, it is what has been found inside the church that has archeologists intrigued.

The church was held together by iron staples that bound the stones to one another, CBS News reported.

The use of iron staples was common in Roman and Greek construction to keep stone blocks in place on lower floors. The staples in Notre Dame, which measure from 10 to 20 inches long and weigh a few kilos, were used to keep walls upright. They were used in the walls of the nave, choir tribunes and cornice, CBS News reported.

Archeologists believe there could be more than a thousand staples throughout the church.

A recent study that describes the use of the staples said the iron connectors were installed in the choir’s checked cornice in 1195 and were not later additions during previous restoration projects. The study did say that there were iron chains and tie rods added to the top of the walls in the choir and upper vaults as part of a mid-19th-century restoration.

Scientists also dated some of the staples, confirming that the iron was cast around the time that Notre Dame was built — from the middle 12th or the beginning of the 13th centuries, the study found.

“Archaeological observations and radiocarbon dating performed on the iron staples sealed on the floor of the tribunes proves that the builders implemented them in the earliest phases of construction, most probably in the early 1160s,” the study’s authors wrote.

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Notre Dame Cathedral fire PARIS, FRANCE - MARCH 06: This statue of Mary, the best-know of the thirty seven representations of the Virgin in Notre-Dame cathedral is displayed during "Notre-Dame de Paris : au cœur du chantier" exhibition on March 06, 2023 in Paris, France. A new underground space in the forecourt of the Notre-Dame de Paris Cathedral in the French capital takes visitors on an educational journey that depict the ongoing construction of the cathedral since the 2019 fire. (Photo by Thierry Chesnot/Getty Images) (Thierry Chesnot/Getty Images)