The Valkhof is on a hill overlooking the river. It is the site of a former Charlemagne fortification and the surviving Carolingian elements are quite modest. There are two buildings with a Carolingian element. The first is an octogon chapel built in the style of Aachen in the 8th or 9th century. The initial building was constructed about 1000 and rebuilt about 1400. It used material from Charlemagne's fortification and we think we could identify some of these Caroilingian flat bricks. The second building is the ruin of Barbarossa's chapel that incorporated several Carolingian capitals on Roman pilars in the chapel.
References:Château de Niort is a medieval castle in the French town of Niort. It consists of two square towers, linked by a 15th-century building and dominates the Sèvre Niortaise valley.
The two donjons are the only remaining part of the castle. The castle was started by Henry II Plantagenet in the 12th century and completed by Richard the Lionheart. It was defended by a rectangular curtain wall and was damaged during the Wars of Religion. In the 18th century, the castle served as a prison.
The present keeps were the central point of a massive fortress. The southern keep is 28m tall, reinforced with turrets. The northern tower is slightly shorter at 23m. Both are flanked with circular turrets at the corners as well as semicircular buttresses. Each of the towers has a spiral staircase serving the upper floors. The Romanesque architecture is of a high quality with the dressed stones closely jointed.