The remains of the Roman town of Regina Turdulorum, found near the municipality of Casas de Reina in Badajoz province, form an extremely interesting ensemble, in a perfect state of preservation, with the forum and a 1st century AD theatre as its most remarkable features.
The Roman theatre was built in the age of the Flavian emperors, could seat one thousand spectators and was operational until the 4th century AD.
Meanwhile Regina's Roman forum preserves the foundations of some houses, civil buildings, porticoes and the odd remnants of paving or Roman road that transport you directly to this period of history. A porticoed templum with a small room dedicated to the worship of the emperor and the imperial house has also been recovered through different excavations, alongside which other buildings must have existed, such as the market and the basilica.
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.