In Assassin's Creed Unity, the Notre-Dame synchronization point is located at Notre-Dame de Paris.
Unity follows Arno Dorian during the French Revolution and gives players a detailed, explorable version of Paris. Synchronization points are elevated locations where Arno surveys the surrounding area; reaching them also reveals nearby map activities and landmarks.
Notre-Dame de Paris, the medieval cathedral on the Île de la Cité, is one of the game's most recognizable buildings. Its inclusion reflects the cathedral's central place in Parisian history and architecture. The game allows players to climb and traverse many landmarks, although its representation is a designed game environment rather than a precise architectural survey.
The Louvre and Les Invalides also appear in Unity, which makes landmark questions easy to mix up. The Eiffel Tower, however, was not yet built during the French Revolution and is not the relevant landmark in the game.