Archéologique Notre-Dame

Entrance staircase to the Crypte Archéologique on the Île de la Cité in Paris, with the sign visible. Kurt Raschke / Wikimedia Commons / CC BY 2.0, above the underground museum entrance

What Is Under the Square in Front of Notre-Dame de Paris?

Beneath the parvis of Notre-Dame lies a 200-metre archaeological crypt containing the layered ruins of three separate cities — Roman, medieval, and 19th-century Paris — stacked on top of each other. Most visitors above never know it is there.