The church of St. Michael (Mihkli) was built in the mid-15th century and it is the biggest one-nave church in Estonia. It was originally constructed as a fortress church; two meter thick walls, narrow windows and the surrounding moat made it easy to defend. The church has been damaged in wars and restored several times.
The unique detail of the Jõhvi church is a great vaulted cellar, which is today renovated as a chapel and museum.
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.