The Greek theatre of Syracuse lies on the south slopes of the Temenite hill, overlooking the modern city of Syracuse. It was first built in the 5th century BC, rebuilt in the 3rd century BC and renovated again in the Roman period. Today, it is a part of the Unesco World Heritage Site of 'Syracuse and the Rocky Necropolis of Pantalica'.
It seems that the theatre was renovated in the third century, transforming it into the form seen today. Its structure was extended, taking into account the shape of the Temenite hill and the best possibilities for acoustics. Another typical characteristic of Greek theatres is the celebration of the panoramic view, also applied to the theatre of Syracuse, offering a view of the bay of the port and the island of Ortygia.
During the Roman era, important modifications were made to the theatre, perhaps at the time when the colonia was founded in the early Augustan period. The cavea was modified to a semicircular form, typical of Roman theatres, rather than the horseshoe used in Greek theatres and corridors allowing access past the scene building (parodoi). The scene building itself was reconstructed in monumental form with rectangular niches at centre and two niches with a semicircular plan on the sides, containing doors to the scene.
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.