While the bishopric has been established since at least the 4th century, the present Acqui Cathedral building was begun under bishop Primo (989-1018) and was consecrated in 1067 by bishop Guido. The ground plan is in the shape of a Latin cross, and there are five aisles (but until the 18th century, only three), terminating in three semi-circular apses. Of the Romanesque structure there still remain visible the apses, the transept, and the crypt, which underlies both the transept and the choir. The remainder has been subject to further work in later centuries.
The terracotta bell tower was finished in 1479, and the bells moved from the old campanile. The main entrance in marble, by Giovanni Antonio Pilacorte, dates from 1481, and the rose window above it from around the same date, while the portico is 17th century. The interior was re-fitted in Baroque woodwork, and was decorated with frescos and stucco work from the 17th to the 19th centuries.
Next door are the canons' cloisters of the late 15th century, and some Roman ruins.
The 19th century pulpit and the Baroque altar of Saint Guido in the transept are worthy of note. The most important work of art in the cathedral by far however is the triptych of the Madonna di Montserrat, the Annunciation to the Virgin of Montserrat, the work of the 15th century Spanish painter Bartolomé Bermejo, in the chapter house.
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.