The Church of the Holy Cross is a medieval Gothic style building with a peculiar shaped tower. Construction started in the 13th century and was completed in the first half of the 15th century. The church was originally built with a round tower, however during the first half of 17th century half of the top of the tower collapsed.
There are two tombs from the 15th century and a pulpit from the 17th century inside the church.
Reference: 7is7.com
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.