Otepää castle hill is the site of an ancient stronghold. It is speculated that a fortified settlement may have existed there even before Christ. The first major extension works were initiated in the 11th and 12th century when the castle was at the crossroads of important trading routes. Herman I, the bishop of Tartu, established there the first stronghold of its diocese. A settlement, which was mainly populated by craftsmen and merchants, appeared around the bishop’s castle in the 13th century. The castle was the first known brick building in Estonia.
References: VisitEstonia, turismiweb.ee
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.