The fortress called "Alexandreion" in Greek, simplified to "Alexandrion" (and Latinised as "Alexandrium"), is mentioned by Josephus in his Antiquities of the Jews.

[4] Alexandrium was constructed by the Hasmoneans near the border with Samaria to accommodate a military garrison, as well as to guard political prisoners.

[5] It is later mentioned during Pompey the Great's conquest of Judea as a stronghold of Aristobulus II: "...as he passed by Pella and Scythopolis, he came to Corem, which is the first entrance into Judea when one passes over the midland countries, where he came to a most beautiful fortress that was built on the top of a mountain called Alexandrium, whither Aristobulus had fled/"[6] The Alexandreion was restored by Herod the Great, a task he assigned to his brother Pheroras.

Herod gave it the character of a palatial desert fortress, similar to those he built or rebuilt at Masada, Herodion and Machaerus.

Herod used the fortress as a prison for his political opponents, holding his 2nd wife, Mariamne and her mother, Alexandra there in 30 BCE.