The Castello di Lombardia iis one of the largest and most ancient edifices in Italy, with an area of some 26,000 m2.
The castle's origins are related to a fortress erected in the 1st millennium BC by the Sicani on the foundation of the ancient Henna, on a hill 970 m above sea level. It remained a key possession in the subsequent history of the island, and the Romans were able to conquer it only by passing through its sewer network.
Under the castle was the ancient Sican temple of Ceres, site of the widespread cult of that goddess in the whole of Italy, which was described by Cicero.
After the fall of the Western Roman Empire, it was used by the Byzantines and resisted Arab assaults for many years. After their victory, the latter rebuilt the fortress around the 10th century; the castle was also used by their successors in Sicily, the Normans. Two centuries later, architect Richard of Lentini was commissioned by Frederick II, Emperor and King of Sicily, to restore it as a summer residence. He added 20 towers and called in a garrison coming from the Langobardia minor (Calabria), whence the castle's name.
With the advent of the artillery, the castle lost its primary strategic role and was turned into a prison. In the 20th and early 21st century, the castle was the site of the Teatro più vicino alle Stelle, used for opera and pop music concerts. The castle is now open to the public.
The Petersberg Citadel is one of the largest extant early-modern citadels in Europe and covers the whole north-western part of the Erfurt city centre. It was built after 1665 on Petersberg hill and was in military use until 1963. It dates from a time when Erfurt was ruled by the Electors of Mainz and is a unique example of the European style of fortress construction. Beneath the citadel is an underground maze of passageways that can be visited on guided tours organised by Erfurt Tourist Office.
The citadel was originally built on the site of a medieval Benedictine Monastery and the earliest parts of the complex date from the 12th century. Erfurt has also been ruled by Sweden, Prussia, Napoleon, the German Empire, the Nazis, and post-World War II Soviet occupying forces, and it was part of the German Democratic Republic (East Germany). All of these regimes used Petersberg Citadel and had an influence on its development. The baroque fortress was in military use until 1963. Since German reunification in 1990, the citadel has undergone significant restoration and it is now open to the public as a historic site.