In ancient times there were very deep valleys surrounding Jerusalem on every side except the north. This made it impossible to attack Jerusalem from any direction except the north side. Herod the Great had determined that the north side needed to be heavily protected. The Antonia Fortress was built on the north side of the Temple in order to protect the vulnerable north side of the city. (It is important to note that Titus Vespasian attacked the city of Jerusalem from the north in 70 A.D.) The Antonia Fortress was located on the northwest corner of the Temple Mount overlooking the Temple area and the city of Jerusalem.