The Bridge of Prado (Ponte do Prado) over the Cávado River was originally a Roman bridge. It was re-constructed during the 16th century when the original had been destroyed following flooding and consistent use. There are few vestiges of the Roman bridge.
The bridge's exit (to the north) fronts the Praça do Conselheiro Sousa Lima, a gardened area, the site of a 16th-century pillory marking Prado's historical importance as a municipality until the 19th century.
The flat-top shallow cantilever bridge consists of nine Roman arches that progressively increase in size the closer to the centre of the span, with the three largest arches slightly peaked. Eight triangular abutments protect the base of the bridge from debris, while polygonal structures downstream act as reinforcements.
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.