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 Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.