Doclea (also Dioclea) was a Roman city, the seat of the Late Roman province of Praevalitana, and an Archbishopric, which is now a Latin Catholic titular see.
The Romanized Illyrian tribe known as Docleatae that inhabited the area derived their name from the city. It was the largest settlement of the Docleatae, founded in the first decade of the 1st century AD. Doclea was built to conform to the terrain. It was a large town with 8–10,000 inhabitants. The surrounding area had a relatively high population density within a radius of 10 km due to the city's geographical position, a favorable climate, positive economic conditions and defensive site that were of great importance at that time.
After the administrative division of the Roman Empire in 297, Doclea became the capital of the newly established Roman province of Praevalitana.
In the 4th and the 5th centuries, it was taken by the barbarian tribes and went into decline. At the beginning of the 5th century, it was attacked by the Germanic Visigoths. A severe earthquake destroyed it in 518. The South Slavs proceeded to rebuild the settlement in the 7th century. The historical ruins of the town can be seen today.
Circa 400, the city became the seat of an archdiocese, apparently Metropolitan as capital of a Late Roman province Dalmatia Superior. It was suppressed in 927. From 1034 till circa 1100, it was nominally united (as a title) with the then still Metropolitan Archdiocese of Bar (Antivari), also in modern Montenegro.
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.