Arch of Trajan in Mérida was an entrance arch, possibly to the provincial forum. It was located in the Cardo Maximus, one of the main streets of the city and connected it to the municipal forum. Made of granite and originally faced with marble, it measures 14 metres high, 5.7 metres wide and 8.7 metres internal diameter. It is believed to have a triumphal character, although it could also serve as a prelude to the Provincial Forum. Its name is arbitrary, as the commemorative inscription was lost centuries ago.
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.