Monzón de Campos Castle was built in the 14th century by the Rojas family on the remains of an earlier castle which was contemporary one. The keep, made of high quality ashlar masonry, has no openings besides a couple of small arrow slits which gives it a severe appearance.
The oldest part is the elevated entrance of the present tower of homage.The coat of arms on the pointed arch of the main gate belongs to the Rojas family.
Inside, the castle has not preserved the original distribution except in the tower. A Romanesque door was added to the tower of homage. It was brought in from a church that had been covered by the water of the dam in Aguilar de Campoo. The village of Monzón, with its castle, was the centre of a county donated to the Ansúrez family by the kings of León during the 10th and 11th centuries and in the 15th and 16th centuries it was owned by the Rojas, a family from Burgos that since 1530 had the title of Marquises of Poza. They are likely to have built the present castle in Monzón de Campos.
References:The Petersberg Citadel is one of the largest extant early-modern citadels in Europe and covers the whole north-western part of the Erfurt city centre. It was built after 1665 on Petersberg hill and was in military use until 1963. It dates from a time when Erfurt was ruled by the Electors of Mainz and is a unique example of the European style of fortress construction. Beneath the citadel is an underground maze of passageways that can be visited on guided tours organised by Erfurt Tourist Office.
The citadel was originally built on the site of a medieval Benedictine Monastery and the earliest parts of the complex date from the 12th century. Erfurt has also been ruled by Sweden, Prussia, Napoleon, the German Empire, the Nazis, and post-World War II Soviet occupying forces, and it was part of the German Democratic Republic (East Germany). All of these regimes used Petersberg Citadel and had an influence on its development. The baroque fortress was in military use until 1963. Since German reunification in 1990, the citadel has undergone significant restoration and it is now open to the public as a historic site.