The Guard Tower is the second best type of tower in Age of Empires. 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. Like all towers, Guard Towers are more resistant against stone throwing siege weapons unlike other buildings, having 18 additional siege armor against them after accounting for building armor. Against Armored Elephants, Guard Towers have 16 extra armor.