The Roman Bridge at Saint-Thibéry was segmental arch bridge on the Via Domitia in southern France. The structure is dated to the reign of emperor Augustus (30 BC – 14 AD). The ancient bridge had nine arches with spans of 10–12 m. The roadway rested on wide piers, which were protected on both sides by arched floodways and large cutwaters. The original length of the structure is estimated as 150 m, its road width as 4 m. The missing spans are known to have been destroyed by flood some time before 1536.
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.