The Aqua Marcia is one of the longest of the eleven aqueducts that supplied the city of Rome. The aqueduct was built between 144–140 BC, during the Roman Republic. The still-functioning Acqua Felice from 1586 runs on long stretches along the route of the Aqua Marcia.
Together with the Aqua Anio Vetus, Aqua Anio Novus and Aqua Claudia, it is regarded as one of the 'four great aqueducts of Rome.'
It was the first to enter Rome on arches, which were used for the last 11 km, and which were also used later combined with the Aqua Tepula and Aqua Julia.
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.