30/09/23 the note is only available when completing the main story quest - Bridge Into the Past
There is a jumping puzzle to get up to the top. The entrance faces out towards the E/SE to the left of the guardian statue. Use the white patches on the stone that indicate the jumping puzzle.
But at the moment it appears that the page is unavailable unless you do the quest. Look to have a friend do the quest if they haven't already, and then use them to open it.
Page can only be acquired during the corpse crone QUEST. The page is inside the chest at the top of the structure. The chest can ONLY be looted during the quest.
quest???
It's on top of a building!
Unlocked with latest patch.