Urkulu (1,419 m) is a mountain in the Basque Country straddling the border between France and Spain. The main feature of the mountain is the remains of a Roman tower topping the summit, erected in the 1st century BC. to commemorate the recent conquest of Aquitaine.
With the summit providing excellent views over the northern and southern slopes alike, it was used as a watchtower in medieval times.
The tower has a truncated-conical shape, measures 19.5 meters in diameter at the base and is 3.6 meters high. Its original height should have been 4.5 meters. The thickness of the walls is 2.6 meters and its interior is filled with the remains of the original stonework.
References: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.