In Age of Empires, the Guard Tower is the second best type of tower. It is available first on the Iron Age, after upgrading the Sentry Tower from the Granary. To research the technology that provides this kind of tower, 300 Food and 100 Stone is required. This unit starts out with 200 hit points, 6 attack and 7 range. The stats can be upgraded. It offers effective defense against other Bronze Age units, but needs to be upgraded to the Ballista Tower to have any kind of effectiveness against Iron Age units. Almost every civilization can build this type of tower. The only exceptions to this are the Romans, the Minoans and the Yamato.