The Antonia fortress was originally the Baris, a strong fortress in Jerusalem near the Temple. It was more strongly rebuilt in 35 B.C. by King Herod to protect the Temple Mount, and is another of Herod's landmarks, overlooking Jerusalem. Located on the Northwest corner of the Temple Mount, it was named after Herod’s friend Marc Antony. It stood 115 feet high and was partly surrounded by a deep ravine 165 feet wide. It functioned as headquarters for the Roman soldiers, as a palace and a barracks. Herod constructed a secret passage from the fortress to the Temple.
The Antonia Fortress was garrisoned with 600 Roman soldiers, who watched over the Temple courts in order to preserve order. The Bible spoke about the Antonia Fortress as a barracks (Acts 21:32-37), and it was here that Paul gave an address to the people (Acts 22:1-21).