Kihnu Church, built in 1784, is one of the few orthodox churches converted from a Lutheran sacral building. Almost all Kihnu people converted to orthodoxy from 1846 to 1847, the Lutheran church was given to the orthodox congregation by order of Tsar Nicholas I and an onion dome was built on the bell tower. Inside the church, you can admire a simple but beautiful iconostasis that covers almost the entire width of the room.
Reference: Visit Estonia
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.