Frias castle origins date back to the 9th century, when Alfonso VIII repopulated the valley to reinforce the border between Castile and Navarre. The historic quarter preserves its medieval atmosphere, and urban layout.
On the tallest, most rugged end of a hill, the castle of the Duke of Frías stands, with its beautiful and well-kept mullioned windows, and 13th-century Romanesque capitals. In the city centre we must point out the church of San Vicente, whose Romanesque main front was taken to New York after the tower fell in 1904, and the convent of Santa María de Vadillo, founded at the beginning of the 13th century.
Near the town, crossing the Ebro river, we see a gorgeous medieval bridge, with a defence tower that dates from the 14th century.
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.