The Romanesque Abbey church was constructed in the mid-11th century and contains many beautiful 11th- and 12th-century murals which are still in a remarkable state of preservation. It has been a UNESCO World Heritage Site since 1983.
The cruciform church carries a square tower over its crossing. The transept was built first, then the choir with its ambulatory with five radial chapels in the polygonal apse. In the next building campaign, three bays of the nave were added, the bell tower and its porch, and finally the last six bays of the nave. The bell tower is finished by a fine stone spire more than 80 meters high, added in the 14th century (and restored in the 19th century).
The barrel vaulted nave is supported on magnificently-scaled column with foliate capitals.
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.