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:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.