The importance of Coria in Roman times is reflected in its defensive military fortification erected during the Early Roman Empire (1st century). Its layout is the shape of an irregular trapezoid featuring solid walls of granite ashlar masonry, completed with the traditional pattern of stretcher and header bond on their faces and the internal reinforcement with a 3-metres-thick layer of concrete. These walls are defended by twenty-three robust square or cube-shaped towers, each located about 20 or 30 metres apart, surrounding its total perimeter of 1,065 metres. The imposing fortification extends across six hectares of land, as the walls adapt to the uneven terrain with their width occasionally exceeding 4 metres and their height ranging between 10 and 14 metres.
These enormous defensive walls protect its boundaries and give access through four entrance gates: to the north, the Puerta de San Pedro/Puerta del Sol (1st century); to the southwest, the Puerta de la Guía/Puerta de la Ciudad (1st century); to the northwest, the Puerta de San Francisco/Puerta del Rollo (16th century); and to the east, the Puerta del Carmen/Puerta Nueva (16th century). These huge gates are reminiscent of the Roman domination and presence in the territory. Although, throughout its extensive history, this borderland has been subjected to alterations and several episodes of war, the Roman City Walls of Coria, as a whole, are arguably among Europe’s best-preserved fortifications.
Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.