The Co-Cathedral of St. Nicholas was built between 1613 and 1662. It was designed between 1610 and 1615 by Agustín Bernardino, a student of Juan de Herrera, and was constructed over an ancient mosque. The older cloister was built originally in the 15th century in Valencian Gothic style.
The cathedral has a Latin cross plan, though the transepts are quite short. Flanking the nave are six interconnecting side chapels and an ambulatory around the apse. A blue dome rises 45 meters above the crossing. The chapel of Holy Communion, configured as a small Greek cross-planned temple, is considered to be one of the most beautiful examples of the Spanish Baroque.
The external appearance of the cathedral is quite sober. The main facade located on the east side is of the Doric order, and the one built on the south side is of Ionic order.
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.