Construction of the St. Nicholas Church began about 1165. It is named after St. Nicholas, patron of travelers and merchants. It was built originally in the Romanesque style (with twin towers) but was extended and enlarged in the early 16th century in the Gothic style. The Baroque main tower was added in 1730; the portal dates from 1759.
From 1784 to 1797 the interior was remodeled by German architect Johann Carl Friedrich Dauthe in the Neoclassical style. The church has been a Protestant seat since 1539 after the Protestant Reformation, but today the Catholic Church is also allowed to use it.
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.