The Vault itself, which can be opened with the combination of a Staff of Eden and an Apple of Eden, contains a holographic map of the world with points labeling other locations, presumably more Vaults.
In 49 BCE, the Order of the Ancients sought to unlock the door to the vault. In their efforts to do so, they abducted the Medjay Bayek and his son Khemu, assuming that the Medjay would have knowledge of Siwa's mysteries. However, Bayek was unaware of the temple, and the following altercation resulted in the death of his son in front of the vault's gates.
By 47 BCE, Flavius Metellus and Lucius Septimius finally managed to unlock the vault with Alexander the Great's Staff of Eden and the Apple of Eden they retrieved from Apollodorus, the very act causing a disturbance that affected all the Siwans. Hepzefa attempted to stop them but was easily killed by Septimius. The two Romans dragged Hepzefa's corpse, where they ripped out his heart as a message to Bayek. After getting their information from the holographic map, they left. Following them, both Bayek and Aya entered the Vault, finding Hepzefa's remains.