The Castle Hill of Grosio is dominated by two castles. The Old Castle (Castello Vecchio) was probably built at the end of the 10th century. The Castello Nuovo was built as a stronghold between 1350 and 1375 due to the military-strategic needs of the 14th century.
The castle is surrounded by a double defense wall and had next to e solid keep even a fortified internal tower. Apart from a military expedition by Giovanni Cane in 1376 to Bormio, which had its starting point here, the Castello Nuovo was never involved in military confrontation or siege. Today the castle is only preserved as a castle ruin because after 1526 the new political power in Valtellina ordered the destruction of all fortifications in the valley. That way the dominion of the Three Leagues wanted to avoid any potential danger that could emanate from their own castles.
During the period of the Bündner Wirren (1620-1639), the Thirty Years' War in Europe, the structure was used by the French under Duke Rohan as a military base and got partially restored. The Castello Nuovo is nowadays the best-preserved example of all the historic defensive structures in the Valtellina.
Between 1992 and 1997 in the area of the Castello Nuovo archaeological excavations could document the remains of a bronze and iron age settlement, dating from the middle of the 2nd to the end of the 1st millennium BC. Some of the small finds are now exposed in the excavation museum.
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.