It was built in the 4th or 5th century, directly in front of the location of the modern cathedral, and 250 meters from the royal residence, the Palais de la Cité.

According to Alain Erlande-Brandenburg, a basilica existed there in 4th century, while Michel Fleury wrote that the cathedral was built later, during the reign of Childebert I (511–558), the son and successor of Clovis, the first French king to convert to Christianity.

The second collateral aisle on the south side was built atop a rampart from the late Roman Empire.

The foundations of another small church, dedicated to Saint Denis, were found just to the east of the chevet of Notre-Dame.

The cathedral also was close to the original Hôtel-Dieu, the first hospital in Paris, built in the 9th century, and later moved to its present location further north.

[7] Vestiges of the foundations of the cathedral are found underneath the parvis, the paved square in front of Notre-Dame de Paris.

(For additional links to the French-language articles, see "Cathédrale Saint-Étienne de Paris" in the French Wikipedia)