Boyana Church is a medieval Bulgarian Orthodox church situated on the outskirts of Sofia. In 1979, the building was added to the UNESCO World Heritage List.
Boyana Church was built in three stages: in the late 10th to early 11th, the mid-13th, and the mid-19th centuries. The oldest section (the eastern church) is a small one-apse cross-vaulted church with inbuilt cruciform supports. It was built in the late 10th or the early 11th century.
The frescoes in this second church, painted in 1259, make it one of the most important collections of medieval paintings. The ensemble is completed by a third church, built at the beginning of the 19th century. This site is one of the most complete and perfectly preserved monuments of east European medieval art.
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.