The Barbara Baths (Barbarathermen) are a large Roman bath complex designated as part of the Roman Monuments, Cathedral of St. Peter and Church of Our Lady in Trier UNESCO World Heritage Site. The Barbara Baths were built in the second century AD. The extensive ruins were used as a castle in the Middle Ages, then torn down and recycled as building material until the remains were used for constructing a Jesuit College in 1610.
Only the foundations and the subterranean service tunnels have survived, but the technical details of the sewer systems, the furnaces, the pools, and the heating system can be studied better than in the other two baths of Trier.
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.