Cathedral comes from the Latin catedra, meaning "seat".
It is the seat of the bishop, whose role it is to administer the diocese but also to teach.
As the majority of the medieval population were illiterate, a cathedral's artworks were a great opportunity to illustrate teachings from the Bible.
The facade was an important part of this, and is often referred to as the "Poor Man's Bible".
High above the doors stand a series of stone figures representing the kings of Judah, the 28 descendants of Abraham.
Fun fact : in 1792, French revolutionaries mistook them for French kings and decapitated them. They have since been restored.
Just above the main door is carved the Last Judgement - when God is said to judge all souls, sending some to heaven and others to hell.
At the bottom, souls are being resuscitated by angels with trumpets.
Above, the archangel Michael is weighing souls on a set of scales - as a demon tries to tip the scales to his side!
The "saved souls" are on the left - pious and relaxed.
The "damned souls" are on the right - led off by demons, scared and in chains.
Importantly, a king, bishop and rich man are being crushed by a demon.
This crucially shows that the Last Judgement applies to all, whether rich, poor, royal or cleric.
Hundreds of spectators are also represented - including Abraham, hiding 3 souls in his tunic!
Jesus is at the top, presiding over the scene, flanked by angels holding the holy cross, nails and lance, the Virgin Mary and Saint John, all praying him to show mercy.
The virtues and vices are represented on each side of the door.
They are at eye-level, to offer a cautionary tale as viewers walked in.
They are also present in other cathedrals, such as Amiens and Chartres.
Strength is represented as a knight holding a shield and a sword. Weakness is represented as a man running away from a rabbit!
Humility is a woman holding a medallion with a bird. Pride is a man falling off his horse.
Wisdom is a woman holding a medallion with a snake, the symbol of medecine. Folly is a man walking barefoot, in the countryside, with a stick that is too short and drinking from his horn.
Perseverance is a monk. Inconsistency is a man running away from the monastery.
Patience is a woman holding a medallion with an ox. Impatience is a young man threatening with his sword another man with a book.
Justice is a woman holding a medallion with a phoenix. Injustice is a man trying to tip the scales in his favour.
Generosity is a woman holding a medallion with a ram. Avarice is a man hiding his money in a safe.
Hope is a woman looking up to the sky. Despair is a man piercing himself with his sword.
Gentleness is a woman holding a medallion with a lamb. Harshness is a man striking his servant.
On each side of the door are also the apostles : Bartholomew, Simon, James, Andrew, John, Peter, Paul, James, Thomas, Philip, Jude and Matthew.