Panoramic View
Synchronize all Viewpoints.

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There are a total of 23 viewpoints that you need to sync, 21 in Paris and 2 in Versailles. Viewpoints are very high points up on the map, and you usually have to climb quite a way to reach them. They are marked on the map with a "" symbol. Once you climb to where the viewpoint is, you will need to press to synchronise. Once you sync a viewpoint, it will reveal all of that area in the district for you. It also reveals chests and side mission locations. Syncing the viewpoints has always been one of the first things I do in Assassin's Creed games as it gives you a clear minimap which will help you a lot. So I recommenced doing this early on. Once you sync the final viewpoint the trophy will unlock.