The Cluilian trench (Latin: Fossae Cluiliae) was a huge military trench that surrounded ancient Rome about four to five miles outside the city made by the army of Alba Longa during the war between Alba Longa and Rome in the middle of the seventh century BC. It was named after the Alban king, Gaius Cluilius.
Livy (Book 2) speaks of the "Cluilian Trenches" again in a battle that took place in the fifth century BC. Here he records Gaius Marcius Coriolanus making use of the Cluilian trenches. He writes that Marcius marched to Circeii and expelled from there the Roman colonists, delivering that city to the Volscians. From there he deprived the Romans of their recently acquired towns of Satricum, Longula, Polusca, Corioli, and Lavinium. Marcius then took Corbio, Vitellia, Trebia, Lavici, and Pedum. Lastly he marched from Pedum to Rome and pitched his camp five miles outside the city at the Cluilian trenches.
Plutarch in his Lives of the noble Grecians and Romans also speaks of these as the "Cluilian ditches" and describes the same battles of Gaius Marcius taking these towns and the siege of Lavinium. He records Marcius marching furiously towards Rome and encamped at a place five miles outside the city called the Cluilian ditches.