There may have been earlier castles at this site, but the Mombeltran castle we see today was built by Don Beltrán de la Cueva, the first Duke of Alburquerque. He placed his coat of arms and those of his successive spouses above the entrance gate. This makes us believe that the construction of the castle took place between 1462 and 1474. The castle was donated to Don Beltrán by King Enrique IV, in 1461. Because there's architectural similarity between this castle and Belmonte Castle and Manzanares el Real Castle its architect probably has been Juan Guas. Although Mombeltrán Castle has a military and defensive appearance there are also many details of luxury for a palatial residence. Also in the 16th century the castle was modified for even more comfort.
Basically the castle is a square of rubblework and granite ashlar masonry with circular towers in the corners. The largest of those towers was the keep which has a central column in its interior on which the floors rest. Around the castle there is a second enclosure which closely follows the outlines of the inner one. This enclosure is equipped with a barbican.
Mombeltrán Castle lies on a beautiful spot, in the mountains of the Sierra de Gredos.
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.