A Pagan City Lies Below The Cathedral.
The Île-de-la-Cité on which Notre-Dame de Paris now stands was once a Gallo-Roman city known as Lutetia. The cathedral may have been built right over remnants of a temple: Around 1710, pieces of a sculpted altar dedicated to Jupiter and other deities were discovered during an excavation under the choir (although it remains unclear if this is evidence of an ancient temple, or if the pieces were recycled there from another location). Additional architectural ruins found in the 1960s and '70s, many dating back to this ancient era, were found in the archaeological crypt located beneath the square just in front of Notre-Dame.
There's A "Forest" In Its Roof.
The cathedral contained one of the oldest surviving wood-timber frames in Paris, involving around 52 acres of trees that were cut down in the 12th century. Each beam was made from an individual tree. For this reason, the lattice of historic woodwork was nicknamed "the Forest."
Twenty-Eight Of Its Kings Lost Their Heads In The French Revolution.
In 1793, in the midst of the French Revolution, 28 statues of biblical kings in the cathedral were pulled down with ropes and decapitated by a mob. (King Louis XVI was guillotined earlier that year, and any iconography tied to the monarchy was under attack.) The mutilated stones were eventually tossed in a trash heap, which the Minister of the Interior dealt with by ordering the material be repurposed for construction. It wasn't until 1977 that the heads of 21 of these kings were rediscovered during work on the basement of the French Bank of Foreign Trade. Now they're at the nearby Musée de Cluny.
The Gargoyles Were New
Some of the most popular images of Notre-Dame are from the perspective of its gargoyles or chimera (the carved monsters that don’t act as waterspouts). Few visitors would guess that the fantastic creatures now on the cathedral weren't there until the 19th century; they were added between 1843 and 1864 during the radical restoration overseen by Eugène-Emmanuel Viollet-le-Duc.