Aqua Anio Novus ('New Anio aqueduct') was an ancient Roman aqueduct. Like the Aqua Claudia, it was begun by emperor Caligula in 38 AD and completed in 52 AD by Claudius.
The aqueduct was split into two channels above Tivoli and combined again near Gericomo. From its filtering tank near the seventh milestone of the Via Latina it was carried on the arches of the Aqua Claudia, in a channel immediately superposed on the latter. It terminated at a great tank on the Esquiline Hill near the temple of Minerva Medici.
As the water was prone to be turbid, Trajan made use of additional sources from the two uppermost of the three lakes formed by Nero for the adornment of his villa at Subiaco, thus lengthening the aqueduct to 58 miles and 700 paces. The lakes were created by dams in the river, and were the tallest of any built by the Romans. They were swept away by the river in the Medieval period.
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.