In Assassin's Creed Unity, which famous Parisian landmark can Arno enter during the campaign?

Notre-Dame Cathedral is the famous Parisian landmark that Arno can enter during Assassin's Creed Unity.

Unity is set in Paris during the French Revolution and allows Arno Dorian to move through a detailed recreation of the city. Notre-Dame appears as an explorable landmark, and the game uses its interior and exterior architecture for missions and traversal.

The cathedral was completed in stages during the medieval period and stood for centuries before the 2019 fire caused major damage. Because Unity was released in 2014, its digital reconstruction has also attracted attention as a historical and architectural reference, although it is still a game-created interpretation rather than a complete architectural survey.

Other Parisian sites appear in Unity, including the Louvre and the Palace of Versailles. Versailles is especially important to the opening portion of the story, but Notre-Dame is the landmark identified by this question. The game also introduced cooperative missions for up to four players.