The Palace of Omurtag is an archaeological site in northeastern Bulgaria dating to Late Antiquity and the Early Middle Ages located near the village of Han Krum in Shumen Province. The site has been pinpointed as the location of a fort and palace of Omurtag, ruler (kanasybigi) of the First Bulgarian Empire in 815–831, as mentioned in the Chatalar Inscription of 822. Earlier structures in the vicinity of the fortress have been identified as the Arian episcopal see of a Gothic bishop.
The main feature of the archaeological site is the early-9th-century Bulgarian fortified rampart with Omurtag's palace within its limits.
The earliest ruins at the Palace of Omurtag site include four churches, two of which built on top of each other; a bath; and fortified walls, all dating to Late Antiquity (roughly 250–650 CE). Three of the churches and the bath lie outside the medieval fortification, while one of the churches and the traces of ancient walls have been excavated within its limits.
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.