Arms and Armour
A castellum in Latin is usually: a small Roman fortlet or tower, a diminutive of castrum ('military camp'), often used as a watchtower or signal station like on Hadrian's Wall. It is distinct from a burgus, which is a later Latin term that was used particularly in the Germanic provinces. a distribution, header, and settling tank for municipal water in a Roman aqueduct (known as a castellum aquae/castellum divisorium). It is the source of the English word "castle".
History of the Great Wall of China.
Harpers Ferry Armory.
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