Canena Castle is a Renaissance building from the 16th century, designed by the Spanish Renaissance architect Andrés de Vandelvira (1509-c. 1575). It belonged to Francisco de los Cobos, private secretary to Charles I and a great patron of the Renaissance in Úbeda and the surrounding area.
The building we see today dates from the 17th century. It adopts an almost square ground plan delimited by two large towers at the ends of the main façade and two smaller and apparently incomplete towers on the rear façade, all them circular. One of the most imposing features is the square keep, which used to be surrounded by a moat, now filled in, and accessed by a drawbridge.
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.