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All Assassin’s Creed: Origins Guides
To investigate the tomb entrance at the tomb of Alexander the great in Aya: Blade of the Goddess in Assassin’s Creed: Origins interact with the spears on the ground. Interact with the door. Go back down the corridor and hit the cracked wall:

To investigate the entrance of the Tomb of Alexander the Great hit the cracked wall.
Interact with the cracked wall and squeeze through the open gap.