Intrigued by tales of Quasimodo, fascinated by the gargoyles, or on a pilgrimage to see the Crown of Thorns said to have rested on Jesus' head on the Cross, more than 13 million people each year flock to see Europe's most popular historic monument.
The 12th century Catholic cathedral is a masterpiece of French Gothic design, with a cavernous vaulted ceiling and some of the largest rose windows on the continent.
It is the seat of the Archdiocese of Paris and its 69m-tall towers were the tallest structures in Paris until the completion of the Eiffel Tower in 1889.
It survived a partial sacking by 16th century zealots and the destruction of many of its treasures during the atheist French Revolution but remains one of the greatest churches in the world and was the scene of Emperor Napoleon's coronation in 1804.
A view of the middle-age stained glass rosace on the southern side of the Notre-Dame de Paris cathedral
The foundation stone was laid in front of Pope Alexander III in 1163, with building work on the initial structure completed in 1260.
The roof of the nave was constructed with a new technology: the rib vault. The roof of the nave was supported by crossed ribs which divided each vault into compartments, and the use of four-part rather than six-part rib vaults meant the roofs were stronger and could be higher.
After the original structure was completed in the mid 13th century - following the consecration of the High altar in 1182 - flying buttresses had been invented, and were added to spread the weight of the mighty vault.
The original spire was constructed in the 13th century, probably between 1220 and 1230. It was battered, weakened and bent by the wind over five centuries, and finally was removed in 1786.
During a 19th century restoration, following desecration during the Revolution, it was recreated with a new version of oak covered with lead. The entire spire weighed 750 tons.
At the summit of the spire were held three relics; a tiny piece of the Crown of Thorns, located in the treasury of the Cathedral; and relics of Denis and Saint Genevieve, patron saints of Paris. They were placed there in 1935 by the Archibishop Verdier, to protect the congregation from lightning or other harm.
The Crown of Thorns was one of the great relics of medieval Christianity. It was acquired by Louis IX, king of France, in Constantinople in AD 1239 for the price of 135,000 livres - nearly half the annual expenditure of France.
The elaborate reliquary in which just one of the thorns is housed sits in the Cathedral having been moved from the Saint-Chappelle church in Paris. The thorn is mounted on a large sapphire in the centre.
The crown itself is also held in the cathedral,
