Battle of Monte Porzio

The Battle of Monte Porzio was fought on 29 May 1167 between the Holy Roman Empire and the Commune of Rome. The communal Roman army, which one historian has called the "greatest army which Rome had sent into the field in centuries", was defeated by the forces of the Emperor Frederick Barbarossa and his local allies, the Counts of Tusculum and the ruler of Albano. Comparing its effect on the city of Rome, one historian has called Monte Porzio the "Cannae of the Middle Ages".
The site of the battle was the field between a small hill and the walls of the city of Tusculum, at a place called "Prataporci", about 25 km southeast of Rome. In his universal chronicle, the Chronica Universalis, the contemporary writer Sicard of Cremona describes the site of battle as "near Monte Porzio" .

Wikipedia