Frötuna Church was built of grey stone in the 12th century. It was extended to east between 1250–1275. The tomb dates from the mid-1600s. There are several medieval aftefacts in Frötuna church, including a triump crucifix (1275), font (1200s) and sculpture of St. Olaf (early 1300s). The pulpit was made in 1640s and the altar dates from 1773.
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.