Mysionis was a large ancient town and fortress. It is located 7 km away of town of Targovishte in region Krumovo Kale, on the northern edge of the steep gorge of the river Vrana in Preslav Mountains.
The site dates back to 6th-7th centuries. After excavations there were found remains of fortress walls 3-4 meters in height, remains of a large church, guard and residential buildings. The slopes of the hills were occupied of neighborhoods and in one of them was found a second large Christian church.
In the vicinity were found also marble columns, antique stone objects, Roman pottery, medieval cemeteries and others. Probably Mysionis existed until the end of the 14th century and was destroyed during the Ottoman invasion.
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.