The Cluilian trench was a huge military trench

Trench warfare

Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely immune to the enemy's small arms fire and are substantially sheltered from artillery...

 that surrounded ancient Rome about four to five miles outside the city made by the army of Alba Longa

Alba Longa

Alba Longa – in Italian sources occasionally written Albalonga – was an ancient city of Latium in central Italy southeast of Rome in the Alban Hills. Founder and head of the Latin League, it was destroyed by Rome around the middle of the 7th century BC. In legend, Romulus and Remus, founders of...

 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

Gaius Cluilius

Gaius Cluilius was the king of Alba Longa during the reign of the Roman king Tullus Hostilius in the middle of the seventh century B.C. Alba Longa was an ancient city of Latium in central Italy southeast of Rome....

.

Livy

Livy

Titus Livius — known as Livy in English — was a Roman historian who wrote a monumental history of Rome and the Roman people. Ab Urbe Condita Libri, "Chapters from the Foundation of the City," covering the period from the earliest legends of Rome well before the traditional foundation in 753 BC...

 (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

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

 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.

Sources

• Livy
  Livy
  Titus Livius — known as Livy in English — was a Roman historian who wrote a monumental history of Rome and the Roman people. Ab Urbe Condita Libri, "Chapters from the Foundation of the City," covering the period from the earliest legends of Rome well before the traditional foundation in 753 BC...
  
  , Ab urbe condita
  Ab urbe condita
  Ab urbe condita is Latin for "from the founding of the City ", traditionally set in 753 BC. AUC is a year-numbering system used by some ancient Roman historians to identify particular Roman years...
  
  , 1:23
• Plutarch: Lives of the noble Grecians and Romans