The original building may have been a wooden tower constructed by Charles the Bald to defend the Grand Pont bridge, later replaced by the Pont au Change. In 1130, Louis VI built a stronger stone fortress on the site, marked by an imposingly tall square tower. It was located in the heart of the city at the Place de Grève.
From 1190, it served as the headquarters of the prévôt de Paris, or provost marshal - essentially the ruler of the city - along with his lieutenants and 48 advisors. Placed in the middle of a then especially sordid district, the Grand Châtelet enjoyed a sinister reputation, much like other judicial institutions of the state.
Justice was carried out swiftly within the prison, which became the source of the word "morgue" in French. In the 15th century, this meant "face" or "to face at". The prison's jailors would stare at the inmates with contempt in order to identify them, should they escape. The word "morgue" thus came to designate the cells.
Throughout the Middle Ages and Renaissance, the Châtelet held prisoners such as the poets François Villon and Clément Marot, and during the 18th century, the highwayman Louis-Dominique Cartouche and the poisoner Antoine François Desrues.
Following the outbreak of the French Revolution, the Châtelet continued to see use as a prison, unlike the Bastille, which was torn down within weeks. The Marquis de Favras was held there in 1790, before being hanged.
In September 1792, Austrian forces marched on Paris. In response, angry revolutionaries stormed the city prisons and massacred the prisoners, who they believed were in league with the foreign armies. On the afternoon of 2 September, the Templar Frédéric Rouille and his thugs marched on the Châtelet. They disarmed the guards and took them prisoner, before taking over the prison and massacring the inmates. While Rouille made his way to the roof to find the warden, the Assassin Arno Dorian infiltrated the building and freed the prison guards. He then assassinated Rouille as the latter taunted the warden.
As the Reign of Terror began and the Law of Suspects was introduced, the Châtelet continued to hold prisoners, while public prosecutor Antoine Fouquier-Tinville took up his office inside. Arno once again infiltrated the building to steal the execution warrant for the Marquis de Sade and save the condemned writer.
Around this time, Jacobin leader Maximilien de Robespierre's spy Didier Paton discovered that the Templars influenced the French government. Upon reporting this to Robespierre, Paton was imprisoned in the Châtelet under the orders of his superior, himself a Templar. In response, Arno and a team of Assassins infiltrated the prison to recover Paton's notebook, which named members of the Templar Order, before rescuing the spy himself.
Around 1795, the swindler Jean-Baptiste Rotondo escaped the Châtelet and fled through the sewers underneath. Before the National Guard could catch the escapee however, Arno killed Rotondo, as the latter was likely to give information on the Assassins to the Templars. Between 1802 and 1810, the Châtelet was demolished under the orders of Napoleon.