The Milvian (or Mulvian) Bridge was an economically and strategically important bridge in the era of the Roman Empire and was the site of the famous Battle of the Milvian Bridge.
A bridge was built by consul Gaius Claudius Nero in 206 BC after he had defeated the Carthaginian army in the Battle of the Metaurus. In 115 BC, consul Marcus Aemilius Scaurus built a new bridge of stone in the same position, demolishing the old one. In 63 BC, letters from the conspirators of the Catiline conspiracy were intercepted here, allowing Cicero to read them to the Roman Senate the next day.
In AD 312, Constantine I defeated his stronger rival Maxentius between this bridge and Saxa Rubra, in the famous Battle of the Milvian Bridge.
During the Middle Ages, the bridge was renovated by a monk named Acuzio, and in 1429 Pope Martin V asked a famous architect, Francesco da Genazzano, to repair it because it was collapsing. During the 18th and 19th centuries, the bridge was modified by two architects, Giuseppe Valadier and Domenico Pigiani.
The bridge was badly damaged in 1849 by Garibaldi's troops, in an attempt to block a French invasion, and later repaired by Pope Pius IX in 1850.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.