The Synagogue of Santa María la Blanca was erected in 1180, according to an inscription on a beam, it is disputably considered the oldest synagogue building in Europe still standing. It is now owned and preserved by the Catholic Church.
Its stylistic and cultural classification is unique among surviving buildings as it was constructed under the Christian Kingdom of Castile by Islamic architects for Jewish use. It is considered a symbol of the cooperation that existed among the three cultures that populated the Iberian Peninsula during the Middle Ages.
The synagogue is a Mudéjar construction, created by Moorish architects for non-Islamic purposes. But it can also be considered one of the finest example of Almohad architecture because of its construction elements and style. The plain white interior walls as well as the use of brick and of pillars instead of columns are characteristics of Almohad architecture. There are also nuances in its architectural classification, because although it was constructed as a synagogue, its hypostyle room and the lack of a women's gallery make it closer in character to a mosque. Though it does not have a women's gallery today, an early twentieth century architect suggested that it did at one time have a one.
The synagogue was turned into a church in 1405 or 1411, but without any major renovations. It took at that time the name of Santa María la Blanca (Saint Mary the White) and today it is most commonly known by this name.
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.