The Arch of Titus was constructed in c. 82 AD by the Emperor Domitian shortly after the death of his older brother Titus to commemorate Titus's victories, including the Siege of Jerusalem (AD 70). The arch has provided the general model for many triumphal arches erected since the 16th century, perhaps most famously it is the inspiration for the Arc de Triomphe in Paris, France.
The Frangipani family turned the arch into a fortified tower in the Middle Ages. It was one of the first buildings sustaining a modern restoration, starting with Raffaele Stern in 1817 and continued by Valadier under Pius VII in 1821, with new capitals and with travertine masonry, distinguishable from the original.
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.